September 28-29, 2013

Malott Hall

University of Kansas Campus

Lawrence, Kansas

Co-Presented by:

Welcome to the 57th Midwest Solid State

Conference! The Local Planning Committee Judy Wu, University of Kansas Jun Li, Kansas State University Hui Zhao, University of Kansas The Advisory Board Wai-Yim Ching, University of Missouri – Kansas City Michael Flatté, University of Iowa Sy-Hwang Liou, University of Nebraska – Lincoln Kieran Mullen, University of Oklahoma

Start End Location Program Book Page #

8:00 8:30 Check-In, Onsite Registration, Poster Setup Hall near 1001 Malott

8:30 8:45 Opening Addresses - Chair: Judy Wu, University of Kansas 1001 Malott Joe Heppert, Jim Guikema, and Hume Feldman

8:45 10:15 Session A - Session Chair: Kieran Mullen, University of Oklahoma 1001 Malott8:45 9:15 (Invited) Xiaobo Chen: Black titanium dioxide nanocrystals 19:15 9:45 (Invited) Jigang Wang: Quantum Femtosecond Magnetism: Magnetic Phase Transition in

Step with Light in a Strongly Correlated Manganese Oxide2

9:45 10:15 (Invited) Stuart Tessmer: Scanning Probe Microscopy of Conducting Protein Nanowires 3

10:15 10:45 Coffee Break Hall near 1001 Malott

10:45 12:30 Session B - Session Chair: Wai-Yim Ching, University of Missouri - Kansas City 1001 Malott10:45 11:15 (Invited) Dan Higgins: Single Molecule Studies of Mesoporous and Graded Silica Films 411:15 11:45 (Invited) Shubhra Gangopadhyay: Controlled growth of sub-2 nm Pt nanoparticles and

size dependent electrical and catalytic properties5

11:45 12:00 Viktor Chikan: Investigation of Fluorescence Emission from CdSe Nanorods in PMMA and P3HT/PMMA Films

6

12:00 12:15 Manashi Nath: Synthesis of Core-shell Type FeSe Nano Materials Encapsulated in 712:15 12:30 Jingbiao Cui: Zinc Oxide Materials with Controlled Properties for Solar Energy 8

12:30 13:15 Lunch Hall near 1001 Malott

12:30 14:15 Poster Session Hall near 1001 MalottPlease see the list of posters at the end of this Schedule. iv-vi

Saturday, September 28, 2013

i

Start End Location Program Book Page #

14:15 16:15 Session C - Session Chair: Hui Zhao, University of Kansas 1001 Malott14:15 14:45 (Invited) Xia Hong: Integrating Graphene with Ferroelectrics 914:45 15:15 (Invited) Bruno Uchoa: Superconducting states in graphene 1015:15 15:30 Arjun Nepal: One-step synthesis of graphene via controlled hydrocarbon detonation 1115:30 15:45 Diego Mastrogiuseppe: Gate-dependent Kondo states in bilayer graphene 1215:45 16:15 (Invited) Hsin-Ying Chiu: Transport and Photoresponse Properties of van der Waals

Heterostructures 13

16:15 18:15 Poster Session and KU Lab Tour Please see the list of posters at the end of this Schedule.

Hall near 1001 Malott and Various Lab Spaces

iv-vi

18:15 18:30 Campus Tour / Walk to Banquet Site KU Campus

18:30 20:30 Conference Banquet Dinner Speaker: Mario A. Medina Announcement of Poster Session Award Winners

Adams Alumni Center

Saturday, September 28, 2013 (continued)

ii

Start End Location Program Book Page #

8:00 8:30 Check-In Hall near 1001 Malott

8:30 9:45 Session D - Session Chair: Michael Flatté, University of Iowa 1001 Malott8:30 9:00 (Invited) Jingyu Lin: Optical and optoelectronic properties of hexagonal boron nitride

epilayers 14

9:00 9:30 (Invited) John Prineas: High-Power, Mid-Infrared Sources from Antimonide-Based III-V Semiconductor Materials

15

9:30 9:45 Shayne Cairns: Topological Transport Studies of Quantum Confined Sb(111) films 169:45 10:00 Jincheng Bai: Investigation of nitrogen-doped graphene as catalyst and catalyst support

for oxygen reduction in both acidic and alkaline solutions17

10:00 10:20 Coffee Break Hall near 1001 Malott

10:20 11:50 Session E - Session Chair: Sy-Hwang Liou, University of Nebraska 1001 Malott10:20 10:50 (Invited) Wai-Yim Ching: Mechanical Properties of Zn and Mg Doped Hydroxyapatite

Crystal18

10:50 11:20 (Invited) Wai-Lun Chan: Probing ultrafast electron transfer at organic semiconductor interfaces

19

11:20 11:35 Donna Kunkel: Organic Topological Ferroelectrics on Noble Metal Surfaces 2011:35 11:50 Michelle Paquette: Exploring Charge Transport in PECVD-Grown Amorphous

Hydrogenated Boron Carbide21

11:50 12:00 Closing Remarks - Jun Li, Kansas State University 1001 Malott

Sunday, September 29, 2013

iii

Poster Number

Poster Title Lead Presenter Program Book Page #

1 Broadband terahertz generation from metamaterials pumped at telecom wavelengths Luo, Liang 222 Accessing the dark exciton states in semiconducting single-walled carbon nanotubes with

THz pulsesLuo, Liang 23

3 Ultrafast Observation of Critical Nematic Fluctuations and Giant Magnetoelastic Coupling in Iron-Pnictides

Patz, Aaron 24

4 Single molecule tracking studies of molecular diffusion in flow-aligned mesoporous silica Chan Park, Seok 255 Impact of Gallium Doping on CdSe Quantum Dots Chikan, Viktor 266 Investigations of Rh Surface-Doped Cr2O3 Nanoparticles Using Raman and

Photoluminescence SpectroscopyAminu, Lukmon 27

7 Synthesis of copper oxide nanoparticles for solar cell applications Bhaumik, Anagh 288 Investigations of the Mechanical Stability of Periodic Mesoporous Silica Materials Brandt, Adam 299 miInvestigations of Al-Doped SBA-15 Periodic Mesoporous Silica Treated in Aqueous

Fluids to High Temperatures and PressuresMaasen, Scott 30

10 Photovoltaic properties of electrochemically deposited Cu2O/ZnO heterojunctions Shang, Mingwei 3111 Investigation of Superparamagnetism & Magnetocaloric effect in FeAs@C Core-Shell

Nanoparticles Desai, Prachi 32

12 Low temperature hydrocarbon-free growth of carbon nanotubes and filled nanofibers by chemical vapor transport

Nath, Manashi 33

13 Patterned growth of vertically ordered nanotube arrays Nath, Manashi 3414 Si-SiO2-Graphene Surface Uran, Serif 3515 Fabrication and characterization of CdS/MWNT/n-Si Transistor Mohammed,

Muatez36

16 A Novel Approach to Josephson Junctions: In Situ Atomic Layer Deposition Elliot, Alan 3717 Atomically Thin Layer MoSe2 on hBN Heterostructure Field-Effect Transistors with Large

PhotoresponseBellus, Matt 38

18 Investigation of Interfacial Interaction between Graphene and MoS2 by Raman Chien, Hui-Chun 3919 Excitonic dynamics in monolayer WSe2 Cui, Qiannan 4020 Vertical Field-Effect Transistor Based on Graphene-MoS2 Heterostructures Kumar, Jatinder 41

Poster Presentations for Saturday, September 28, 2013

iv

Poster Number

Poster Title Lead Presenter Program Book Page #

21 Dynamics of excitons in monolayer and bulk MoSe2 studied by transient absorption microscopy

Kumar, Nardeep 42

22 Graphene-based hybrid structure for transparent conductive electrodes Liu, Jianwei 4323 In-situ Fabrication of Plasmonic Gold Nanoparticles on Graphene for Surface Enhanced

Raman SpectroscopyLu, Rongtao 44

24 Highly Epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 Thin Films for Energy Application Ma, Chunrui 4525 Conformal coating of vertically aligned carbon nanofiber arrays via atomic layer deposition Malek, Gary 4726 Pulsed Laser Deposition of Thin Film CdTe/CdS Solar Cells with CdS/ZnS Superlattice Meeth, Jake 4827 Assembling Heterostructures with Clean Interfaces between hBN and Other van der Waals

MaterialsSicilian, David 49

28 Fabrication and Charactetization of InGaAs Metal-Oxide-Semiconductor Capacitors with HfO2 Dielectrics

Wenderott, Jill 50

29 Classification of CSH Crystals via a Quantum Mechanical Metric Dharmawardhana, Chamila

51

30 Thermo-mechanical Properties of Mo5Si3 (T1 Phase)-based Alloys Dharmawardhana, Chamila

52

31 A Neural Network Based Approach to Self-Consistent Field Calculations in ab initio Electronic Structure Calculations

Dari, Naseer 53

32 A Multi-method Approach to Modeling Amorphous Hydrogenated Boron Carbide Cramm Horn, Rachel

54

33 Computational Study of a Model of Type I Collagen and Implementation of an Amino Acid Potential Method Applicable to Large Proteins

Eifler, Jay 55

34 Mobility–Lifetime Product Measurement in Amorphous Hydrogenated Boron Carbide Using the Steady-State Photoconductivity Method

Hurley, Justin 56

35 Mobility Measurements of Amorphous Hydrogenated Boron Carbide Utilizing the Dark-Injection Space-Charge-Limited Current Method

Keck, Christopher 57

36 Oxidation of Cr2AlC (0001): Insights from ab initio calculations Li, Neng 5837 Crystal Structure and Elastic Properties of MAX-like (Cr2Hf)2Al3C3 Mo, Yuxiang 5938 Laser ablation of Ge in liquid in electric field Musaev, Omar 60

v

Poster Number

Poster Title Lead Presenter Program Book Page #

39 Monitoring an Orthocarborane Plasma for Amorphous Hydrogenated Boron Carbide Film Growth using Optical Emission spectroscopy

Nguyen, Thuong 61

40 Controlling the dielectric and electronic properties of PECVD-grown amorphous hydrogenated boron carbide thin films

Nordell, Bradley 62

41 Calculation of Charge Distribution of Doxorubicin in Water Poudel, Lokendra 6342 Implementation of Accurate Relativistic Theory in the ab initio Orthogonalized Linear

Combination of Atomic Orbitals MethodThomas, Patrick 64

43 Density Functional Development and Selection in the ab initio Density Functional Theory Based Orthogonalized Linear Combination of Atomic Orbitals Method

Thomsen, John 65

44 Implementation of a 3-Center Mulliken Overlap Population Analysis Method Walker, Benjamin 6645 X-Ray Absorption Near Edge Structure of Crystalline Elemental Boron Wang, Liaoyuan 6746 Electronic structure, Mechanical and Optical properties of CaO•Al2O3 system: A First

Principles StudyHussain, Altaf 68

47 Self-assembled Structurally Complex Double-layers of 3-HPLN on Cu(111) Beniwal, Sumit 6948 Microresonator Magnetic Sensor Jiao, Qianqian 7049 Graphene Field effect Sensors for the Study of Ferroelectric Thin Films Rajapitamahuni,

Anil71

50 Domain wall roughness and creep in nanoscale crystalline ferroelectric polymers Xiao, Zhiyong 7251 Novel Magnetic Nanostructured Multilayer for High Sensitive Magnetoresistive Sensors Yin, Xiaolu 73

vi

Black titanium dioxide nanocrystals Xiaobo Chen

Department of Chemistry, University of Missouri - Kansas City, MO, 64110 Email: chenxiaobo@umkc.edu

Titanium dioxide (TiO2) is well known for photocatalytic hydrogen generation, photocatalytic CO2 conversion, and photocatalytic environmental cleanings. Its ability to absorb sunlight plays a key role in the overall efficiency in these applications. However, TiO2 is a white material, with a large bandgap, and only absorbs light in the ultraviolet (UV) region. This limits the efficiency of TiO2 in the renewable energy applications using natural sunlight, as the UV part only accounts for less than 5% of the whole solar spectrum. Here, I would like to present our study on how to turn white titanium dioxide into black, in order to improve its efficiency in renewable energy applications. The fundamental materials and physiochemical characterizations will be discussed in details.

References [1] X. Chen, L. Liu, P. Y. Yu, S. S. Mao Science 2011, 331, 746. [2] T. Xia, X. Chen, J. Mater. Chem. A 2013, 1(9), 2983 - 2989. [3] T. Xia, W. Zhang, W. Li, N.A. Oyler, G. Liu, X. Chen Nano Energy 2013, DOI:

/10.1016/j.nanoen.2013.02.005. [4] X. Chen, L. Liu, Z. Liu, M. A. Marcus, W.-C. Wang, N. A. Oyler, M. E. Grass, B. Mao, P.-

A. Glans, P. Y. Yu, J. Guo, S. S. Mao, Sci. Rep. 2013, 3, 1510. [5] L. Liu, P. P. Yu, X. Chen, S. S. Mao, D. Z. Shen, Phys. Rev. Lett. 2013, 111, 065505.

Page 1

Quantum Femtosecond Magnetism: Magnetic Phase Transition in Step with Light in a Strongly Correlated

Manganese Oxide

J. Wang* Dept of Physics and Astronomy, Iowa State University and Ames Laboratory, Ames, IA

*E-mail: jwang@ameslab.gov Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal highly non-equilibrium, “thermodynamically hidden” orders during femtosecond timescales? There is growing evidence that femtosecond laser-induced transient polarization can be used to manipulate magnetic order during a laser pulse [1]. Recently we explored this by a new paradigm called quantum femtosecond magnetism—photoinduced femtosecond magnetic phase transitions driven by quantum spin flucations correlated with laser-excited inter-atomic bonding coherences [2, 3]. We demonstrate such quantum fs magnetic phase change in step with fs laser pulse in a in a strongly-correlated colossal magneto-resistive manganese oxide Pr0.7Ca0.3MnO3. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior. This reveals magnetic switching during 100 fs laser pulses, from antiferromagnetic (AFM) to ferromagnetic (FM) ordering, while the optical polarization/coherence still interacts with the spins. Such far-from-equilibrium many-body problems involve an extremely poorly-understood interplay between quantum coherence, strong correlation and nonlinearity. This research thus provides a new framework to seek the ultimate switching speed of magnetic and electronic phases in strongly correlated oxides, and raises fundamental questions regarding some accepted rules of phase transitions, including the cornerstone concepts of free energy and adiabatic potential surface.

References [1] M. D. Kapetanakis, et al., “Femtosecond Coherent Control of Spins in (Ga,Mn)As

Ferromagnetic Semiconductors Using Light,” Physical Review Letters, 103, 047404 (2009); [2] T. Li, A. Patz, L. MouChliadis, J. Yan, T. A. Lograsso, I. E. Perakis, and J. Wang,

“Femtosecond switching of magnetism via strongly correlated spin–charge quantum excitations,” Nature, 496, 69 (2013)

[3] R. Won, “Magneto-optics: Femtosecond switching,” Nature Photonics, 7, 423 (2013)

This work in done in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso and Ilias E. Perakis.

Page 2

Scanning Probe Microscopy of Conducting Protein Nanowires

Stuart Tessmer1 1Michigan State University, Department of Physics and Astronomy, tessmer@msu.edu

Nanoscale protein filaments, or pili, from the bacterium Geobacter sulfurreducens act as electrically conductive nanowires. The pili have dimensions similar to carbon nanotubes: a few nanometers in diameter, yet up to several microns in length. They transport metabolically generated electrons outside the cell body to electron acceptors in the organism's environment. The mechanism of the conductivity in these protein-based filaments is a topic of considerable debate. Here I will present scanning probe microscopy images with molecular-scale resolution and transport measurements of the pili, to elucidate this fascinating system.

Page 3

Single Molecule Studies of Mesoporous and Graded Silica Films

Daniel A. Higgins Department of Chemistry, Kansas State University, 213 CBC Bldg, Manhattan, KS,

66506-0401. Email: higgins@ksu.edu

Mesoporous silica materials have a broad range of applications in energy-related fields and are being investigated for use as catalysts, as separator membranes in fuel cells and batteries, and as stationary phases for chemical separations. Enhanced selectivities are achieved in these applications by controlling the steric and chemical interactions between the reagents or analytes and the pore surfaces. By tailoring the pore dimensions, species larger than a certain size can be prevented from entering the materials, while others readily pass through them. By manipulating the chemical functionality of the pore surfaces, other physical and chemical interactions can be employed to further enhance selectivity: electrostatic, hydrophilic, hydrophobic and/or hydrogen bonding interactions can all be used to control solution-phase mass transport. However, before any of these materials can be fully developed for commercial use, much remains to be learned about the fundamental molecular-level mechanisms of mass transport within them. In particular, the effects of nanoconfinement on the properties of incorporated solvents and solutes represents an area of intense interest.

We employ single molecule tracking (SMT) methods as a means to better understand molecular diffusion, surface interactions and the effects of nanoconfinement within mesoporous silica materials. This presentation will review a subset of our recent work in this area.[1] Studies in which SMT methods have been used to observe and characterize 1D probe molecule diffusion within cylindrical silica mesopores will be discussed. These methods have been used to quantitatively assess local mesopore order within individual ordered domains, and to obtain valuable knowledge on the origins of materials disorder. Recent polarization-dependent SMT studies will also be covered. These reveal that the orientational motions of the probe dyes are highly restricted within the silica pores, with the dye molecules exhibiting confined wobbling-like motions. Quantitative measurements of the single molecule wobbling angles and the accessible cavity diameters reveal that the molecules are confined to cavities that are much smaller than the physical pore dimensions. It is concluded that nanostructuring of the solvent-filled pore medium plays a significant role in limiting molecular motions. Finally, wavelength-resolved SMT studies of organically modified silica gradients will also be covered. These studies provide an in-depth view of interactions between model reagents/analytes and chemically modified silica surfaces. The results provide semi-quantitative data on the local film viscosity and polarity properties relevant to reagent partitioning and surface interactions.

References [1] D. A. Higgins, K.-H. Tran-Ba and T. Ito, “Following Single Molecules to a Better

Understanding of Self-Assembled One-Dimensional Nanostructures”, J. Phys. Chem. Lett. In press.

Page 4

Controlled growth of sub-2 nm Pt nanoparticles and size dependent electrical and catalytic properties

Shubhra Gangopadhyay Dept. of Electrical and Computer Engineering,

University of Missouri, Columbia

Sub 2 nm Pt nanoparticles with highly controllable size distributions and number densities have been developed at MU using a tilted target sputtering (TTS) technique. Control on Pt nanoparticle growth characteristics are controlled by varying incident sputtered atom flux densities, degree of thermalization, energy of incident atoms/clusters and surface energy of the substrate. Due to narrow size distributions, size dependent properties of these Pt nanoparticles can be studied and based on this study, nanoparticle size dependent applications in a variety of fields can be explored. It has been observed that while sub nm non-crystalline Pt clusters have charge trapping characteristics, Pt nanoparticles bigger than ~ 1.3 nm in diameter show fast charge transfer characteristics. Some of the applications of these sub 2 nm sputtered Pt nanoparticles in electronic devices and catalysis will be presented.

Page 5

Investigation of Fluorescence Emission from CdSe Nanorods in PMMA and P3HT/PMMA Films Lorinc Sarkany,† Jenna M. Wasylenko,‡ Santanu Roy,† Daniel A. Higgins†,*,

Christopher G. Elles,‡,* and Viktor Chikan†,* †Department of Chemistry, Kansas State University, Manhattan, KS, 66506-3701

‡Department of Chemistry, University of Kansas, Lawrence, KS, 66045-7572 Complementary fluorescence microscopy and ultrafast transient absorption spectroscopy measurements spanning a range of timescales from seconds to femtoseconds probe the interfacial dynamics of charge carriers in CdSe nanorod/polymer blends. Together, these very different techniques provide new information about the origin and dynamics of below-bandedge [1] emission from CdSe nanorods in CdSe/PMMA and CdSe/P3HT/PMMA films [PMMA = poly(methyl methacrylate); P3HT = poly(3-hexylthiophene)]. Emission below the bandedge of the CdSe nanorods is associated with surface defects (traps)[2] at the nanoparticle/polymer interface, where conduction band electrons radiatively relax to the intraband defect sites. The fluorescence microscopy experiments simultaneously monitor both the trap emission and the bandedge emission from single nanoparticles, and reveal that the two emission channels are distinct. Transitions between the two emissive states occur on timescales longer than ~20 ms, and always involve an intermediate dark state in which no emission is observed. The presence of P3HT increases the relative bandedge emission intensity and reduces the fluorescence intermittency (blinking) of both emissive states. The ultrafast transient absorption experiments monitor the evolution of a stimulated emission band below the CdSe bandedge following excitation of P3HT. The measurements reveal ultrafast electron transfer from photoexcited P3HT to the CdSe nanorods within the instrument response time of approximately 140 fs, and confirm that there is strong coupling between the nanorods and P3HT in these dilute blends. Analysis of separate CdSe nanorod etching experiments suggests that the trap states are formed by the removal of atoms from the ends of the nanorods in the presence of chloroform. Mechanisms for charge trapping at the nanoparticle/polymer interface are discussed.

References [1] Roy, S.; Aguirre, A.; Higgins, D. A.; Chikan, V., Investigation of Charge Transfer

Interactions in Cdse Nanorod P3ht/Pmma Blends by Optical Microscopy. J. Phys. Chem. C 2012, 116, 3153-3160.

[2] Lorinc Sarkany, Jenna M. Wasylenko, Santanu Roy, Daniel A. Higgins, Christopher G. Elles, and Viktor Chikan Investigation of Fluorescence Emission from CdSe Nanorods in PMMA and P3HT/PMMA Films. J. Phys. Chem. C 2013, in press

Page 6

Synthesis of Core-shell Type FeSe Nano Materials Encapsulated in Carbon

Wipula P. R. Liyanage, Manashi Nath*

Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409 *Email: nathm@mst.edu

Abstract – Since the discovery of superconductivity in iron based compounds, tetragonal iron selenide, has drawn a considerable attraction because it has the simplest crystal structure among Fe based superconductors and also due to the fact that the Tc in this family is very sensitive to variation in pressure and morphology. The authors have previously shown that the Tc can be increased by trapping FeSe in nanostructures. The present study proposes a new method for synthesizing FeSe coated composite nanomaterials (typically nanorods and nanoparticles) through Pd-catalyzed simple chemical vapor transport reactions at 800°C from volatile precursors, iron acetylacetonate and elemental Se. Morphology controlled Pd nanoparticles were used as catalysts and the reaction conditions were varied to obtain different thicknesses of the (conformal) FeSe coating. The product morphology and composition were characterized through powder X-ray diffraction, SEM, HRTEM, SAED and EDX with elemental mapping. The dependence of Tc for these nanostructures on the thickness and the morphology of the FeSe coating will be discussed with respect to the magnetic characterization. These nanomaterials can serve as ideal systems to study the effect of morphology and interfacial pressure on superconducting properties, while the method offers an easier and faster fabrication process to generate these superconducting FeSe-based nanomaterials.

Figure 1: SEM image of FeSe-Pd composite nanorods encapsulated in carbon (inset: HRTEM image showing the phase segregation between FeSe and Pd-rich zones.)

Page 7

Zinc Oxide Materials with Controlled Properties for Solar Energy Applications

Jingbiao Cui1, Allan Thomas2, and Johnathan Armstrong1 1Department of Physics and Astronomy, University of Arkansas at Little Rock, Arkansas

72204. Email:jxcui@ualr.edu 2Department of Physics and Engineering Physics, University of Tulsa, Oklahoma 74104

Photovoltaics based on nanowires are considered as the next generation solar cells,

which are still in their initial development stage. Fabrication of nanowire solar cells are challenging due to the complicated device structures and the needed materials with well controlled properties. This presentation will cover the recent progress made on ZnO, one of the important solar cell materials, and its applications in nanowire solar cells. ZnO thin films and nanowires have been doped by a variety of dopants in order to tune their physical properties to meet the requirements of specific applications such solar cells. The dopant materials used in this study include Ag, Al, H, and Mg by using both processes of electrochemical and atomic layer deposition [1,2]. The structural, optical, and electrical properties of the various ZnO were characterized by techniques such as scanning electron microscopy, atomic force microscopy, x-ray diffraction, photoluminescence, transmission/absorption, and resistivity and Hall effect measurements. The electrical properties of the doped ZnO are shown to be readily tunable to have either n or p-type conductivity. In our ALD process, in-situ plasma treatments were used with standard thermal-ALD processes, which is capable of significantly reducing or increasing the n-type conductivity in ZnO by employing either an O2 or H2 plasma, respectively. The resistivity is controllable within more than eight orders of magnitude ranging from 7 x 10-

4 to 1 x 105 Ωcm. Al-doped ZnO (AZO) and Zn1-xMgxO films are also readily obtained by inserting an appropriate number of Al2O3 or MgO cycles in between the standard ZnO growth sequence. By adjusting the number of dopant cycles the optical and electrical properties of ZnO can also be well controlled. These materials can serve as excellent candidates for use as n-type layers, buffer layers, intrinsic layers, and conductive window layers in solar cells, especially copper indium gallium sulfide (CIGS) and copper zinc tin sulfide (CZTS) devices. Nanowire solar cells based on solution processed CIGS absorber in combination with various ZnO materials will be presented. Challenges and opportunities for nanowire solar cells will also be discussed.

References [1] M.A. Thomas, J. Armstrong, J.B. Cui, “A New Approach Toward Transparent and

Conductive ZnO by Atomic Layer Deposition: Hydrogen Plasma Doping”, Journal of Vacuum Science and Technology A31, 01A130-1/6 (2013).

[2] M.A. Thomas, J.B. Cui, “Highly Tunable Electrical Properties in Undoped ZnO Grown by Plasma Enhanced Thermal-Atomic Layer Deposition”, ACS Applied Materials and Interfaces 4, 3122-3128 (2012).

Page 8

Integrating Graphene with Ferroelectrics Xia Hong

Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 (xhong2@unl.edu)

With the recent observations of enhanced functionalities of graphene via interfacing with various dielectric materials, it is of intense fundamental and technological interest to examine graphene-functional dielectrics hybrid devices. Integrating graphene with ferroelectrics allows one to explore graphene-based nanoelectronics such as high frequency analog devices and nonvolatile memories. One can also use graphene as a sensitive tool to probe the properties of nanoscale ferroelectric thin films, where conventional electrical characterization becomes challenging.

In this talk, I will discuss our recent effort on integrating graphene with ferroelectric thin films to incorporate memory and sensor functionalities into graphene devices. [1-4] We have studied graphene field effect devices gated by epitaxial ferroelectric Pb(Zr,Ti)3 (PZT) and (Ba,Sr)TiO3 (BSTO) thin films. Using graphene as a sensor, we have examined the dielectric, pyroelectric, and ferroelectric properties of the ferroelectric gate. For BSTO-gated graphene, we observe a crossover behavior in the resistance switching from ferroelectric polarization induced hysteresis at low temperature to an anti-hysteresis dominated behavior above 100 K, in sharp contrast with the PZT-gated devices, which exhibit anti-hysteresis dominated switching for the whole temperature range. We attribute such observations to the competition between ferroelectric polarization and interfacial screening charge dynamics. [2-4] Graphene field effect devices can potentially be used to study a range of technologically important phenomena such as pyroelectricity, piezoelectricity and flexoelectricity at the nanoscale, where surface polarization charge is a critical parameter. Our work also reveals the important roles played by the polarization field and interface chemistry on the electronic behavior of graphene. [2-4]

References [1] X. Hong et al, “High-mobility few-layer graphene field effect transistors fabricated on

epitaxial ferroelectric gate oxides”, Phys. Rev. Lett. 102, 136808 (2009). [2] X. Hong et al, “Unusual resistance hysteresis in n-layer graphene field effect transistors

fabricated on ferroelectric Pb(Zr0.2Ti0.8)O3”, Appl. Phys. Lett. 97, 033114 (2010). [3] X. Hong et al, “Integrating functional oxides with graphene”, Sol. Stat. Commun. 152, 1365

(2012). [4] A. Rajapitamahuni et al, “Examining Graphene Field Effect Sensors for Ferroelectric Thin

Film Studies”, Nano Lett., in press, DOI: 10.1021/nl402204t (2013).

Page 9

Superconducting states in graphene Bruno Uchoa

Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 uchoa@nhn.ou.edu

In this talk, I will discuss the experimental prospects for the observation of intrinsic superconductivity in graphene. After a brief review of the classification of symmetry states in the honeycomb lattice and general thermodynamic properties for Dirac fermion superconductors, I will discuss different possible mechanisms. I will make the case that one promising possibility is applying strain fields, which can create time reversal invariant Landau levels with massively large degeneracies. I will show that superconductivity is this system is quantum critical at integer filling factors. At partial filling, the quenching of the kinetic energy due to Landau level quantization leads to a crossover to a non-Fermi liquid regime, where the critical temperature scales linearly with the coupling in the weak coupling limit. The critical temperature can be orders of magnitude larger than in conventional weak coupling superconductors, and may be triggered by phonons.

Page 10

One-step synthesis of graphene via controlled hydrocarbon detonation

Arjun Nepal,1 (anepal@phys.ksu.edu) Gajendra P. Singh,1,2 Bret N. Flanders1 and C. M.

Sorensen1 1Department of Physics, Kansas State University, Manhattan, Kansas-66506, USA 2Centre for Nanotechnology, Central University of Jharkhand, Ranchi-835205, Jharkhand, India Gram quantities of pristine graphene nanosheets (GNs) were produced via one-step detonation of gas-phase hydrocarbon (C2H2). The detonation of C2H2 was carried out in the presence of O2. The molar ratios of O2/C2H2 were 0.4, 0.5, 0.6, 0.7, and 0.8 [1] The obtained GNs were analyzed by XRD, TEM, XPS and Raman spectroscopy. The GNs are crystalline with (002) peak centered at 26.05° (d = 0.341 nm). TEM shows that the GNs are stacked in two to three layers and sometimes single layers. An increase in the size of GNs (35-250 nm) along with reduction in defects (Raman ID/IG~ 1.33- 0.28) and specific surface area (187 to 23 m2g-1) was found with increasing O2 content. The method allows for the control of the number of layers, shape and size of the graphene nanosheets and the process can be scaled up for industrial production.

References [1] A. Nepal et al, “One-step synthesis of graphene via catalyst-free gas-phase hydrocarbon

detonation”, Nanotechnology 24(2013) 245602.

Page 11

Gate-dependent Kondo states in bilayer graphene D. Mastrogiuseppe1,2 , A.Wong3, K. Ingersent3, S. Ulloa1,2 and N.

Sandler1,2

1 Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701-2979, USA (mastrogi@ohio.edu)

2 Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany

3 Department of Physics, University of Florida, P.O. Box 118440, Gainesville, Florida, 32611-8440, USA

One of the remarkable manifestations of cooperative phenomena in condensed matter physics is the many-body screening of a magnetic impurity placed in a metallic system, the Kondo effect. Although the physics underlying this effect in ordinary metals is well understood, microscopic symmetries can give rise to intricate features in the effective density of states of the host with profound consequences in the Kondo regime. Bilayer graphene (BLG) is an example of such a material with a gate-dependent gap and large pseudospin symmetry that provides an ample set of different microscopic environments for intercalated magnetic impurities. Combined to its easy tunability, BLG is an ideal material to study quantum phase transitions into various types of Kondo states.

We provide a full characterization of these transitions for a magnetic impurity intercalated in Bernal-stacked BLG and symmetrically coupled to carbon atoms on each layer, as a function of doping level of the system. Two factors determine the wealth of phases predicted: 1) the particular dispersion relation of BLG that gives rise to an interesting density of states with a discontinuity at the interlayer hopping energy; and 2) the properties of the microscopic coupling between the impurity and the layers that define different symmetries for the possible phases.

A multiband Anderson Hamiltonian that includes interaction and different hybridization environments describes the system. After an appropriate Schrieffer-Wolff transformation, we find the effective single-channel Kondo model with a strongly energy-dependent exchange coupling between conduction electron and impurity spins. This effective Kondo Hamiltonian reveals the possibility of driving the system through quantum phase transitions via changes in the chemical potential through gating or doping.

We use numerical renormalization group calculations to accurately describe the Kondo regime. Our calculations reveal zero-temperature transitions between local-moment and singlet strong-coupling phases under variation of band filling and/or energy of the impurity level. We also obtain the Kondo temperature dependence with the chemical potential within the different regimes, which would be accessible via STM experiments.

Page 12

Transport and Photoresponse Properties of van der Waals Heterostructures

Hsin-Ying Chiu1,*, Matthew Z. Bellus1, Jatinder Kumar1, David L. Sicilian1, Hui-Chun Chien1, Benjamin I. Weintrub1, A. Davis St. Aubin1,

T. B. Hoffman2, Y. Zhang2, and J. H. Edgar2 1Department of Physics and Astronomy, University of Kansas, 2Department of Chemical

Engineering, Kansas State University, *e-mail: chiu@ku.edu The feasibility of creating various kinds of van der Waals heterostructures has brought much attention recently as an emerging research topic in the nanoscience and nanotechnology. In this talk, the following topics will be covered: (1) fabrication of ultrathin heterostructures with van der Waals materials, (2) the issue of hydrocarbon residue as contaminants at interface of heterostructures, and (3) transport and photoresponse properties of both MoSe2/hBN and MoS2/graphene/hBN heterostructures.

Page 13

Optical and optoelectronic properties of hexagonal boron nitride epilayers

Jingyu Lin and Hongxing Jiang

Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409

Hexagonal boron nitride (hBN) possesses extraordinary physical properties including high temperature stability, dielectric strength, optical absorption, negative electron affinity, neutron capture cross section and corrosion resistance. Its energy band gap is comparable to AlN (Eg ~ 6 eV). Moreover, hBN is a material with a very low dielectric constant, but having a very high dielectric strength. Due to its layered structure and similar lattice constants to graphene, hBN is also highly suitable for use as a template in graphene electronics and as a gate dielectric layer and provides an ideal platform to study fundamental properties of layer-structured materials. Hexagonal BN epilayers have been synthesized by metal organic chemical vapor deposition (M)CVD). These MOCVD grown epilayers exhibit highly efficient band-edge photoluminescence (PL) emission lines centered at around 5.5 eV at room temperature. The results represent a remarkable improvement over the optical qualities of hBN films synthesized by different methods in the past. It was observed that the emission of hBN is more than two orders of magnitude higher than that of high quality AlN epilayers. Polarization-resolved PL spectroscopy revealed that hBN epilayers are predominantly a surface emission material, in which the band-edge emission with electric field perpendicular to the c-axis (𝐸 𝑒𝑚𝑖 ⊥ c) is about 1.7 times stronger than the component along the c-axis (𝐸 𝑒𝑚𝑖 ∥ 𝑐) [1,2]. This is in contrast to AlN, in which the band-edge emission is known to be polarized along the c-axis, (𝐸 𝑒𝑚𝑖 ∥ 𝑐). Based on the graphene optical absorption concept, the estimated band-edge absorption coefficient of hBN is about 7x105/cm, which is more than 3 times higher than the value for wurtzite AlN (∼2x105 /cm). The dielectric strength of hBN epilayers exceeds that of AlN and is greater than 4.4 MV/cm based on the measured result for an hBN epilayer released from the host sapphire substrate. The hBN epilayer based DUV detectors exhibit a sharp cut-off wavelength around 230 nm, which coincides with the band-edge PL emission peak and virtually no responses in the long wavelengths. Mg doped hBN epilayers grown on insulating AlN templates were p-type with an in-plane resistivity of ~ 2.3 Ω cm. Diode behavior in the p-n structures of p-hBN/n-AlxGa1-xN (x∼0.62) has been demonstrated [3]. These results represent a major step towards the realization of hBN based practical devices. The efforts on hBN MOCVD growth and hBN emitter works are supported by DARPA-CMUVT program (FA2386-10-1-4165); the effort on the fundamental optical studies of hBN is supported by DOE (FG02-09ER46552); and the hBN detector work is supported by DHS (2011-DN-077-ARI048-02). References: [1] S. Majety, X. K. Cao, J. Li, R. Dahal, J. Y. Lin and H. X. Jiang, “Appl. Phys. Lett. 101, 051110 (2012). [2] R. Dahal, J. Li, S. Majety, B.N. Pantha, X.K. Cao, J.Y. Lin, and H.X. Jiang, Appl. Phys. Lett. 98, 211110 (2011). [3] S. Majety, J. Li, X. K. Cao, R. Dahal, B. N. Pantha, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 100, 061121 (2012).

Page 14

High-Power, Mid-Infrared Sources from Antimonide-Based III-V Semiconductor Materials

John P. Prineas 1Dept. Of Physics and Astronomy, and Optical Science and Technology Center,

University of Iowa, Iowa City, IA 52242

There has been much excitement over 2-5 µm infrared lasers, including quaternary lasers, interband cascaded lasers, W lasers, and intraband quantum cascade lasers, but scant attention paid to high power light emitting diodes (LEDs). However, there are a growing number of applications where high power LEDs are needed, and where laser diodes are not useful. For example, in point optical sensing of biomolecules, broadband emitters are needed over several hundred nanometers to measure the broad molecular resonances in aqueous solutions. In thermal scene generation, flat panel displays consisting of a million pixel arrays must use threshold-less devices to be practical. Here, development of 2-2.6 um GaInAsSb LEDs and 3-5 um InAs/GaSb LEDs will be described, including cascaded surface emitters and edge emitting superluminescent diodes.

Research into limiting nonradiative mechanisms, both Shockley-Read-Hall and Auger, in these antimonide-based III-V materials will also be presented. GaInAsSb on GaSb is metastable or unstable over about 2-4 ums, a large swath of its range. However, nonequilibrium growth techniques and strain can be used to grow it with good miscibility and quality over its entire compositional range. In InAs/GaSb superlattices, Auger scattering, usually dominant in mid-infrared materials at high current densities, can be very effectively suppressed by appropriate choice of layer thickness, making SRH recombination potentially a limiting mechanism even at high carrier density. In InAs/GaSb superlattices, work to date suggests SRH recombination is due to native point defects, and not interface roughness, a previous focus of much research and development.

Page 15

Topological Transport Studies of Quantum Confined Sb(111) films

S. Cairns, N. Teasdale, N. McGlohon, J. Keay, C.K. Gaspe, K.S. Wickramasinghe, T.D. Mishma, M.B. Santos, S.Q. Murphy

Homer L. Dodge Physics and Astronomy, University of Oklahoma, Norman, OK (scairns@cox.net)

Sb is a topological semi-metal with a negative bandgap of 180meV, however it is anticipated that in ultra-thin films, quantum confinement will open the bulk gap, such that transport is dominated by the topological surface states. We have studied the magneto-transport of ~nominally 1.5 nm to 3.2 nm thick films of Sb(111) grown via molecular beam epitaxy [2] at a temperature of 280 Co on nearly lattice matched epilayers. Scanning electron microscopy shows that the Sb growth yielded smooth and continuous films that show reduced bulk conduction at low temperatures. The longitudinal resistance shows positive magneto-resistance, well described by the standard weak anti-localization (WAL) theory of Hikami, Larkin and Nagaoka [1]. At high fields the magneto-resistance shows a growing linear magneto-resistance (LMR) as the film thickness is decreased. The origins of the LMR are discussed. A low field resistance jump is observed around 25 mT. This jump originates from an interaction of the In contacts (which are superconducting at the measurement temperature of 300 mK) and the topological surface states of the Sb layer. Further projects are being researched to explore this superconducting proximity effect and other quantum interference effects.

References [1] Hikami et al, “Spin-Orbit Interaction and Magnetoresistance in the Two Dimensional

Random System”, Progress of Theoretical Physics 63, 707 (1980). [2] Gaspe et al, “Epitaxial Growth of Elemental Sb Quantum Wells”, Journal of Vacuum Science

& Technology 31, 03C129 (2013).

Page 16

Investigation of nitrogen-doped graphene as catalyst and catalyst support for oxygen reduction in both acidic

and alkaline solutions Jincheng Bai1, 2 and Lifeng Dong2*

1College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, PR China

2Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, MO, 65897, USA, LifengDong@Missouristate.edu

Fuel cells are promising energy devices which are able to convert chemical energy to electrical energy with low pollutant emission and high energy conversion efficiency. However, the performance of fuel cells depends greatly on oxygen reduction reaction, which is substantially affected by the activity of cathode catalyst. In order to solve the slow kinetics of oxygen reduction reaction, carbon materials such as carbon nanotubes and graphene have been utilized as catalyst supports for fuel cells. In this study, graphene and nitrogen (N)-doped graphene were synthesized through a solvothermal method and investigated as catalysts as well as catalyst supports for oxygen reduction reactions. Electrochemical measurements demonstrated that N-doped graphene possessed higher electrocatalytic activity than graphene in both acidic and alkaline solutions. N-doped graphene can directly act as a catalyst to facilitate four-electron oxygen reductions in alkaline solution but two-electron reductions in acidic solution. On the other hand, when employed as catalyst supports for platinum (Pt) and Pt-ruthenium (Ru) nanoparticles, N-doped graphene can contribute to four-electron oxygen reductions in acidic solution, yet in alkaline solution the kinetics of reduction reaction is much slow. Our conclusion is that N-doped graphene can work as an efficient catalyst for oxygen reductions to substitute the precious Pt catalysts in alkaline solution and catalyst support for Pt and Pt-Ru catalysts in acidic solution.

Page 17

Mechanical Properties of Zn and Mg Doped Hydroxyapatite Crystal

W. Y. Ching1, K. Matsunaga2, Sitaram Aryal1 1Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri

64110. Email: chingw@umkc.edu 2Department of Materials Science and Engineering, Nagoya University, Aichi 464-8603,

Japan. Hydroxyapatite (HAP) is an important bioceramic which constitutes the mineral components of bones and hard tissues in mammals. It is bioactive and is used as bioceramic coatings (i.e. in metallic implants) and bone fillers. HAP readily absorbs impurities so stoichiometric HAP is rare. The change in the elastic and mechanical properties of impurity-doped HAP is a subject of considerable importance. Zn and Mg are the most common divalent cations HAP absorb. Using ab initio methods, we calculated elastic and mechanical bulk properties of a large 352 atoms supercell HAP crystal with Zn or Mg doped in different concentration at the Ca1 and Ca2 sites. Our calculations show that Mg enhances overall bulk mechanical properties of HAP whereas Zn degrades except in low concentration. At higher concentration, the mechanical properties depend significantly on impurity distribution between the Ca1 and Ca2 sites. Zn and Mg form relatively strong bonds with O atoms in PO4 and also with the OH groups, disrupting the ordered alignment of the structure along the crystallographic c-axis. Lattice constant c decreases almost linearly with Mg concentration and is independent of Mg distribution between Ca1 and Ca2 sites. In the case of Zn substitution, c remains nearly constant and independent of Zn distribution between the Ca1 and Ca2 sites only for lower Zn concentration. The density of the dopped crystal increases linearly with Zn concentration with a large drop in the elastic constant C33 resulting in degradation of bulk mechanical properties. For substitution by Mg, the density remains pretty much constant with a small decrease in C33 leading to enhanced mechanical bulk properties. These and other results will be presented and discussed.

Page 18

Probing ultrafast electron transfer at organic semiconductor interfaces

Wai-Lun Chan1, John R. Tritsch2, X. –Y. Zhu3 1Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045

(wlchan@ku.edu) 2Texas Materials Institute, University of Texas at Austin, Austin, TX 78701 3Department of Chemistry, Columbia University, New York City, NY 10027

Electron transfer at the interface between two materials is a critical process to the functioning of many devices such as photovoltaics, photodetectors, and photocatalyst. However, the ultrafast electron transfer rate is difficult to measure because most of the existing ultrafast probes are not interface specific. Recently, we demonstrate that by using time-resolved photoemission technique, we can resolve the rates of competitive electron transfer and relaxation channels of photo-excited electrons at the interface between two organic semiconductors. Two problems related to organic photovoltaics that are studied by this technique will be present. First, the rate of multiple electron transfer at the tetracene/C60 interface originated from singlet fission is measured, which shows that singlet fission can potentially raise the solar cell efficiency beyond the conventional limit [1]. Second, the competition between relaxation and charge transfer of hot charge transfer excitons at the CuPC/C60 interface is discussed; demonstrating that charge separation at this donor/acceptor interface is most efficient within the first few ps after the charge transfer [2]. References [1] W. L. Chan, J. R. Tritsch, X. –Y. Zhu, “Harvesting singlet fission for solar energy

conversion: one versus two electron transfer from the quantum mechanical superposition”, J. Am. Chem. Soc.134, 18295 (2012).

[2] A. E. Jailaubekov, A. Willard, J. R. Tritsch, W. –L. Chan, N. Sai, R. Gearba, L. G. Kaake, K. J. Williams, K. Leung, P. J. Rossky, and X. –Y. Zhu, “Hot Charge Transfer Excitons Set the Time Limit for Charge Separation at Donor/Acceptor Interfaces in Organic Photovoltaics”, Nature Materials 12, 66 (2013).

Page 19

Organic Topological Ferroelectrics on Noble Metal

Surfaces

D.A. Kunkel1, J. Hooper

2, S. Simpson

2, S. Beniwal

1, E. Zurek

2 and A.

Enders1

1University of Nebraska at Lincoln, Dept. of Physics and Astronomy,

donna.ann.kunkel@gmail.com 2State University of New York at Buffalo, Dept. of Chemistry

With the recent discovery of proton-transfer type ferroelectricity in croconic acid [1],

intense interest has been generated into novel organic ferroelectrics which rely on

switchable hydrogen bonds [2]. For many of these crystals, including croconic acid, only

a single, mono-layer thick sheet is necessary for proton transfer since the electric

polarization is in the plane of each hydrogen bonded sheet. As such, we present surface

supported motifs of two organic molecules, croconic acid and rhodizonic acid, which are

part of a family of oxocarbons including squaric acid and deltic acid, all of which only

vary by the number of carbon atoms in the central ring. Scanning tunneling microscopy

experiments explore the self-assembly, chirality, and surface chemistry for these

molecules on the (111) facets of Au, Ag, and Cu. We find that both croconic and

rhodizonic acid form two dimensional networks which differ sharply from their bulk

crystals [3], with surface catalyzed deprotonation occurring on Cu(111)[4]. The

structure, electronic properties and electric polarization of these systems is investigated

by density functional theory, which finds that the substrate enables a spontaneous

polarization by lowering the switching barrier thus enabling spontaneous proton transfer.

References

[1] S. Horiuchi, et al, “Above-room-temperature ferroelectricity in a

single-component molecular crystal” Nature, 463, 789 (2010).

[2] S. Horiuch, et al, “Hydrogen-Bonding Molecular Chains for High-Temperature

Ferroelectricity” Adv. Mat., 23, 2098 (2011).

[3] D.A. Kunkel, et al, “Proton transfer in surface-stabilized chiral motifs of croconic acid” Phys.

Rev. B, 87, 041402 (2013)

[4] D.A. Kunkel, et al “Rhodizonic Acid on Noble Metals: Surface Reactivity

and Coordination Chemistry” submitted.

Page 20

Exploring Charge Transport in PECVD-Grown Amorphous Hydrogenated Boron Carbide

Michelle M. Paquette,1 Christopher L. Keck,1 Bradley J. Nordell,1 Thuong D. Nguyen,1 Justin D. Hurley,1 Sudarshan Karki,1 Emeshaw Ashenafi,2 Rachel Cramm Horn,1 Paul Rulis,1 Sudhaunshu Purohit,3

Nathan A. Oyler,3 Sean W. King,4 and Anthony N. Caruso1 1Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas

City, MO 64110; paquettem@umkc.edu 2Department of Computer Science and Electrical Engineering, University of Missouri-

Kansas City, Kansas City, MO 64110 3Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110

4Logic Technology Development, Intel Corporation, Hillsboro, OR 97124

Boron carbide is an intriguing solid comprised of boron-based icosahedra connected by three-atom chains; its electron density is delocalized across the icosahedra, which are bound together by strong intermolecular bonds. The electrical transport mechanism in crystalline or polycrystalline boron carbide, B4C, has remained a controversial topic for decades, its origin rooted in electron deficiency and defects intrinsic to the solid. Experimentally, B4C is a p-type semiconductor with moderate resistivities (10–2 – 102 Ω cm). PECVD-grown amorphous hydrogenated boron carbide (a-BxC:Hy), however, displays resistivities more than ten orders of magnitude higher, upwards of 1012 Ω cm. This combination of high resistivity with additional properties unique to boron-rich solids such as a very high 10B thermal neutron capture cross section, low density, high hardness, and high chemical stability, render PECVD-grown a-BxC:Hy a suitable candidate for specialized next-generation semiconductor or nanoelectronics applications requiring ultra-low leakage currents, including solid-state neutron detection and low-k dielectric layers in interconnect systems. To advance these applications, understanding and ultimately optimizing the electronic structure and electrical carrier transport properties (e.g., band gap, defect profile, mobility, charge carrier concentration, recombination lifetime, etc.) of a-BxC:Hy is critical. The PECVD-grown amorphous material shares some similarities with its crystalline counterpart, in particular the icosahedral subunit, but it also exhibits differences, including disorder, hydrogenation, and carbon-atom substitution. Herein, measured electrical carrier transport properties of a-BxC:Hy are reported, and models for its physical and electronic structure are used as a basis for interpreting the observed electrical transport behavior.

Page 21

Broadband Terahertz Generation from Metamaterials

Pumped at Telecomm Wavelengths

Liang Luo1, Ioannis Chatzakis

1, Jigang Wang

1*, Fabian B. P. Niesler

2,

Martin Wegener2, Thomas Koschny

1, and Costas M. Soukoulis

1, 3*

1Department of Physics and Astronomy and Ames Laboratory—U.S. DOE, Iowa State

University, Ames, Iowa 50011, USA (JW: jgwang@iastate.edu) 2Institute of Applied Physics, Institute of Nanotechnology, and DFG-Center for

Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), 76128

Karlsruhe, Germany 3Institute of Electronic Structure and Lasers (IESL), FORTH, 71110 Heraklion, Crete,

Greece (CMS: soukoulis@ameslab.gov)

The Terahertz spectral regime ranging from about 0.1 to 15 THz (1 THz = 1012

Hz), is

one of the least explored yet most technologically transformative spectral regions [1].

One key current challenge is to develop efficient and compact THz emitters/detectors

with a broadband and gapless spectrum that can be tailored for various pump photon

energies. Recently, the development of metamaterials composed of split ring resonators

(SRRs) has enabled researchers to tailor resonant optical nonlinearities from the THz to

the infrared and visible regions [2]. While nonlinear metamaterials have been actively

pursued [3], THz generation from any type of metamaterial has not been reported. Here

we demonstrate efficient single-cycle, broadband THz generation, ranging from about 0.1

to 4 THz, from a thin layer of SRRs with few tens of nanometers thickness by pumping at

the telecomm-wavelength of 1.5 μm (200 THz) of the ultrafast laser pulses. The THz

emission arises from exciting the magnetic-dipole resonance of SRRs and quickly

decreases under off-resonance pumping. This, together with pump polarization

dependence and power scaling of the THz emission, identifies the role of optically

induced nonlinear currents in SRRs. We reveal a giant sheet nonlinear susceptibility of

~10-16

m2/V that far exceeds thin films and bulk non-centrosymmetric materials such as

ZnTe [4-6].

References

[1] M. Tonouchi, “Cutting-edge terahertz technology”, Nature Photon. 1, 97-105 (2007).

[2] C. M. Soukoulis & M. Wegener, “Past achievements and future challenges in the development

of three-dimensional photonic metamaterials”, Nature Photon. 5, 523-530 (2011).

[3] C. M. Soukoulis, S. Linden & M. Wegener, “Negative refractive index at optical

wavelengths”, Science 315, 47-49 (2007).

[4] F. Kajzar & J. D. Swalen, “Organic Thin Films for Waveguiding Nonlinear Opitcs” (Gordon

and Breach, Amsterdam, 1996).

[5] Th. Rasing & I. Musevic, “Surfaces and Interfaces Liquid Crystals” (Springer-Verlag, Berlin,

2004).

[6] F. J. Rodriguez, F. X. Wang & M. Kauranen, “Calibration of the second-order nonlinear

optical susceptibility of surface and bulk of glass”, Opt. Express 16, 8704-8710 (2008).

Page 22

Accessing the Dark Exciton States in Semiconducting Single-Walled Carbon Nanotubes with THz Pulses

Liang Luo1, Ioannis Chatzakis1, Jigang Wang1* 1Department of Physics and Astronomy and Ames Laboratory—U.S. DOE, Iowa State

University, Ames, Iowa 50011, USA (JW: jgwang@iastate.edu)

Singled-walled carbon nanotubes (SWCNTs) represent a model system to systematically investigate correlated charge excitation in 1-D limits [1]. One of the most outstanding issues both in fundamental nanotube physics and for their technological development is to detect and understand optically-forbidden, dark collective states [2]. Thus far supporting evidence of dark states has been demonstrated in static magneto-optics and light scattering [3]. However, the unique internal transitions from dark excitonic ground states and their dynamic evolution remain highly elusive. We report our investigation of this problem using optical pump, terahertz probe spectroscopy of (6,5) and (7,5) SWNTs. We measure transient THz conductivity from 0.5-2.5 THz (2-10.5 meV) at low temperature down to 5 K with resonant and off-resonant excitation at the E22 transitions of (6,5) and (7,5) nanotubes. These results reveal, for the first time, dynamics of lowest dark excitons and density-dependent renormalization of these many-particle states. The internal-excitonic spectroscopy with THz pulses represents a fundamentally new spectroscopy tools to study dark excitons and shine new lights on the correlation physics of excitonic ground states.

References

[1] M. S. Dresselhaus, G. Dresselhaus, R. Saito & A Jorio, “Exciton Photophysics of Carbon Nanotubes”, Annu. Rev. Phys. Chem. 58, 719 (2007).

[2] J. Maultzsch et al, “Exciton binding energies in carbon nanotubes from two-photon photoluminescence”, Phys. Rev. B 72, 241402(R) (2005).

[3] A. Srivastava, H. Htoon, V. I. Klimov & J. Kono, “Direct observation of dark excitons in individual carbon nanotubes: inhomogeneity in the exchange splitting”, Phys Rev. Lett. 101, 087402 (2008).

Page 23

Ultrafast Observation of Critical Nematic Fluctuations and Giant Magnetoelastic Coupling in Iron-Pnictides

A. Patz1, T. Li1, S. Ran1, R.M. Fernandes2, J. Schmalian3, S.L. Bud’ko1, P.C. Canfield1, I.E. Perakis4, and J. Wang1,*

1Dept of Physics and Astronomy, Iowa State University and Ames Laboratory, Ames, IA 2School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 3Institute for Theory of Condensed Matter Physics and Center for Functional

Nanostructures, Karlsruhe Institute of Technology, Karlsruhe, Germany 4Dept of Physics, University of Crete, Haraklion, and Institute of Electronic Structure &

Laser, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece *E-mail: jgwang@iastate.edu, jwang@ameslab.gov

A significant anisotropy is manifested in the normal state properties of many of the Iron-pnictides, and has emerged as a crosscutting challenge for understanding complexity in advanced materials, quantum magnetism and high-Tc superconductivity [1-3]. Although an electronically driven tetragonal symmetry breaking (electronic nematicity) has been invoked, its distinction from spin and structural orders is still hindered as they couple together to break the same symmetry [4]. Time-resolved laser techniques have the unique capability to temporally separate the various order parameters, revealing their interplay. Here, we use femtosecond-resolved polarimetry to reveal critical fluctuations of nematic correlation in unstrained Ba(Fe1−xCox)2As2. The anisotropic response, which arises from the two-fold in-plane anisotropy of the refractive index, displays a characteristic two-step recovery following pump excitation. The fast recovery appears only in the magnetically ordered state, whereas the slow one persists into the paramagnetic phase with a sharp increase of the relaxation time approaching the structural transition temperature, indicative of the critical divergence of nematic fluctuations. This behavior is absent in the isotropic response from lattice and electron dynamics. Particularly, the ultrafast dynamics reveal a gigantic magnetoelastic coupling that far exceeds electron (e)-spin and e-phonon couplings, opposite to conventional magnetic metals. This establishes an independent electronic nematic degree of freedom in iron pnictides, and bridges the gap between unconventional quantum nematic matter [5] and technologically relevant functionalities.

References [1] Tanatar, M. A. et al, “Uniaxial-strain mechanical detwinning of CaFe2As2 and BaFe2As2

crystals: Optical and transport study”, Phys. Rev. B 81, 184508 (2010) [2] Chu, J. et al., ”In-Plane Resistivity Anisotropy in an Underdoped Iron Arsenide

Superconductor”, Science 329, 824 (2010) [3] Nakajima, M. et al, “Unprecedented anisotropic metallic state in undoped iron arsenide

BaFe2As2 revealed by optical spectroscopy”, Proc. Natl. Acad. Sci. 108, 30 (2011) [4] Fernandes, R.M. et al, “Preemptive nematic order, pseudogap, and orbital order in the iron

pnictides”, Phys. Rev. B 85, 024534 (2012) [5] Fradkin, et al, “Nematic Fermi Fluids in Condensed Matter Physics”, Annu. Rev. Cond. Mat.

Phys. 1, 153-178 (2010).

Page 24

Single molecule tracking studies of molecular diffusion in flow-aligned mesoporous silica monoliths Seok Chan Park1, Takashi Ito1 and Daniel A. Higgins1

1 Department of Chemistry, Kansas State University, Manhattan, KS 66506-04019

(schpark@ksu.edu)

Single molecule diffusion in surfactant-templated mesoporous silica monoliths prepared within microfluidic channels is probed by total internal reflection fluorescence (TIRF) microscopy. In initial studies, the alignment of mesoporous silica monoliths prepared by flow alignment of surfactant templated silica sols were investigated as a function of sol aging time prior to loading into the microfluidic channels.1 Cetyltrimethylammonium bromide (CTAB) was employed as the surfactant and an uncharged fluorescent perylene diimide dye (OPDI) was employed as the probe molecule. Wide-field fluorescence videos depict one-dimensional (1D) motion of the dyes within the individual cylindrical mesopores. Orthogonal regression analysis of these motions provides a measure of the mesopore orientation distribution function. Channels filled prior to gelation of the sol are shown to incorporate large monodomains having average pore alignment within a few degrees of the flow direction. In contrast, channels filled close to or after gelation yield monoliths with misaligned pores that are also more disordered.

More recently, Pluronic F127 has been utilized as the surfactant template and the diffusive motions of dyes that are uncharged, cationic and anionic were explored.2 The single molecule tracking (SMT) studies for the uncharged dye showed development of 1D diffusion along the flow direction as a function of aging time after filling of the microfluidic channels. SMT results reveal a difference in single molecular motion and the diffusion rate of the three probe molecules in these materials. The origins of this behavior will be discussed.

References

[1] S. C. Park et al, “Single Molecule Tracking Studies of Flow-Aligned Mesoporous Silica Monoliths: Aging-Time Dependence of Pore Order”, J. Phys. Chem. B 117, 4222 (2013)

[2] S. C. Park et al, unpublished.

Page 25

Impact of Gallium Doping on CdSe Quantum Dots

Christopher Tuinenga1, Santanu Roy2, Heather, Shinogle3, Shenqiang Ren3, Alec Kirkeminde3, David Moore3 and Viktor Chikan2*

1) United States Army Research Laboratory, Aberdeen Proving Grounds, Aberdeen,

Maryland 2) Department of Chemistry, Kansas State University, Manhattan, KS 66506,

3) Kansas University, Microscopy and Analytical Imaging Lab, Lawrence, KS 66045

Semiconductor quantum dots exhibit fascinating and important physical and chemical

properties that can hold the potential to play crucial role in transforming the photovoltaic

industry[1], creating new business opportunities and producing electricity to address the

increasing global energy needs. Doping quantum dots to increase their conductive

properties will be vital to creating a new generation of devices. CdSe quantum dots have

been doped with gallium to provide donor electrons greater access to the conduction

band[2]. Gallium doped quantum dots show significantly different electronic properties

than undoped quantum dots. The increased ability for donor electrons to populate the

conduction band levels of quantum dots will make it possible to fabricate more efficient

devices.

References [1] Chikan, V., Challenges and Prospects of Electronic Doping of Colloidal Quantum Dots:

Case Study of CdSe. J. Phys. Chem. Lett. (2011), 2 (21), 2783-2789. [2] Santanu Roy, C. T., Fadzai Fungura, Pinar Dagtepe, Jacek Jasinski and Viktor

Chikan, Progress towards Producing n-type CdSe Quantum Dots: Tin and Indium Doped CdSe Quantum Dots. J. Phys. Chem. C (2009), 113 (30), 13008–13015.

Page 26

Investigations of Rh Surface-Doped Cr2O3 Nanoparticles Using Raman and Photoluminescence Spectroscopy

Lukmon Aminu1, Robert A. Mayanovic1, Adam Brandt1, Steven Harrellson1 1Department of Physics, Astronomy and Materials Science, Missouri State University,

Springfield, MO 65897 (ola1@live.missouristate.edu) Photocatalysis is potentially a useful means of conversion of solar energy to the production of hydrogen fuel from splitting of water. Although several metal oxides have been shown to have photocatalytic activity, most are limited because of their inefficiency. In order to use metal-oxide-based materials as photocatalysts, it is necessary to increase their efficiency. The use of noble metals, either through doping or co-deposition, has shown promise for increasing the overall efficiency of metal-oxide-based nanomaterials. Using our hydrothermal methods, we have precipitated Rh (i.e., surface-doping) on Cr2O3 nanocrystalline material. The Rh surface-doped Cr2O3 nanoparticles were prepared in water at temperatures up to ~220 °C. Surface doping of nanophase materials with noble metals such as Rh has advantages in a more efficient use of a rare commodity and, in our case, is shown to cause greater structural phase stability of the nanoparticles than using bulk doping. Raman spectroscopy shows that the E1

g mode occurring at 276 cm-1 for Cr2O3 nanoparticles is shifted to 281 cm-1 for Rh surface-doped Cr2O3 nanoparticles. The photoluminescence of the Rh surface-doped Cr2O3 nanoparticles in the visible range (~500 – 650 nm) is significantly enhanced relative to that of Cr2O3 nanoparticles, suggesting that surface precipitation of Rh may cause more efficient photocatalytic activity of the Cr2O3 nanomaterial.

Page 27

Synthesis of copper oxide nanoparticles for solar cell applications

Anagh Bhaumik1 and Kartik Ghosh1

1Department of Physics, Astronomy and Materials Science, Missouri State University,

Springfield, MO 65897, USA. Email id: ana123@live.missouristate.edu

Copper oxide nanoparticles are increasingly used in various applications such as solar

energy transformation, magnetic phase transitions, gas sensors, catalysts, superconductors,

and nanomedicines. The worldwide quest for a clean, renewable and economical source of

energy has encouraged an extensive research in the field of solar cells. Solar cell

technology, as a sustainable source of energy, has enjoyed a tremendous growth in recent

years and production of solar cells increases at an annual average of ~ 40% [1].Copper

oxide compounds as a p-type semi-conductors provide a unique possibility to tune the

optical and electronic properties from insulating to metallic conduction, from band gap

energies of 2.1eV to the infrared at 1.4eV, i.e. right into the middle of the maximum

efficiency for solar-cell applications. With the decrease of the crystallite size of the copper

oxide particles to the nanoparticles range, it exhibits unique physical and chemical

properties from those of their bulk materials and thereby enhances its performance in the

currently existing applications. Metal oxide nanoparticles have special physiochemical

properties arising from the quantum size effect and a high specific surface area which may

be different from their bulk counterparts [2].

We have prepared nanoparticles of copper oxides by a cost effective hydrothermal

process using coppersulphate penthydrate as the precursor. The shape and size as well as

the phase of the copper oxide can be engineered by altering the pH, reaction temperature,

and time. The following SEM Images are taken for copper oxides formed at different

reaction temperatures and time, using different bases (NaOH, KOH and NH4OH). Different

morphology of nanostructures are visualized like pollen grains, flakes and rods. The

structural, phase identification, molecular vibrational modes, optical properties and

morphology was determined by using XRD, Raman Spectroscopy, PL,UV-Visible

spectroscopy and SEM.

SEM images (a-c) of copper oxides showing various microstructures created through

changing pH of the mixture, growth temperatures, and growth times. Mapping of copper

oxide (d) sample formed after hydrothermal treatment. The red dots represent copper rich

areas whereas the green dots resemble oxygen rich areas in the sample.

References:

[1] A.Jager-Waldau, Solar Energy, 667, 77 (2004)

[2] A Chowdhuri, V Gupta and K Sreenivas, “Response speed of SnO2-based H2S gas

sensors with CuO Nanoparticles”, Applied physics Lett. 84, 1180 (2004)

a b c d

2µm 2µm 1µm 5µm

Page 28

Investigations of the Mechanical Stability of Periodic Mesoporous Silica Materials

Adam Brandt1, Hao Yan1, Robert A. Mayanovic1, Zhongwu Wang,2 Manik

Mandal3, Kai Landskron3 1Department of Physics, Astronomy and Materials Science, Missouri State University,

Springfield, MO 65897, USA,(brandt230@live.missouristate.edu)

2 Cornell High Energy Synchrotron Source, Wilson Laboratory, Cornell University, Ithaca, NY

14853 3 Department of Chemistry, Lehigh University, Bethlehem, PA 18015

In situ small angle synchrotron x-ray scattering (SAXS) measurements were made on periodic

mesoporous silica materials as a function of pressure to determine their mechanical stability.

The measurements were made using the diamond anvil cell at beam line B1 of the Cornell High

Energy Synchrotron Source (CHESS). The samples were loaded in the diamond anvil cell under

atmospheric conditions. The measurements were made on mesoporous FDU-12 silica, having the

Fm3m pore structure with a unit cell parameter of 34.8 ± 0.3 nm, and on mesoporous SBA-16

silica, having the Im3m pore structure with a unit cell parameter at 0 GPA of 13.6 0.3nm. The

SAXS measured from a periodic mesoporous FDU-12 silica sample indicated a steady reduction

in ordering of the pore structure up to ~ 3 GPa and a leveling off behavior above that value. The

volume compressibility of the FDU-12 mesoporous silica estimated from the pressure-

dependence of the 111 peak yields a value of 5.6 ± 1 GPa. In situ SAXS of periodic mesoporous

SBA-16 silica with carbon filled pores indicates that this material has high mechanical strength.

We estimate the volume compressibility of the carbon-filled periodic mesoporous SBA-16 silica

to be 19.4 ± 2 GPa.

Page 29

miInvestigations of Al-Doped SBA-15 Periodic Mesoporous Silica Treated in Aqueous Fluids to High Temperatures and

Pressures

Scott Maasen1, Adam Brandt1, Robert A. Mayanovic1, Steven Harrellson1 1Department of Physics, Astronomy and Materials Science, Missouri State University,

Springfield, MO 65897 (Scott001@live.missouristate.edu) Modification of the physical and chemical properties of SBA-15 periodic mesoporous silica by surface-doping with metal ions such as Al3+ using hydrothermal methods has potential applications in the energy and chemical industry. Our objectives in this research project are to investigate the structural, vibrational and optical properties of Al-surface-doped SBA-15 periodic mesoporous silica. A reactor vessel built out of Hastelloy C-276 material was used to react Al(III) with SBA-15 periodic mesoporous silica under hydrothermal conditions at temperatures ranging from 100 to 170 °C. The SBA-15 is a mesoporous silica sieve based on uniform hexagonal pores with a pore diameter of 30 - 40 nm. Doping with Al was accomplished using a solution prepared from Al(H2O)6Cl3 dissolved in deoxygenated, doubly distilled water. The vibrational and photoluminescence properties of Al-surface-doped SBA-15 periodic mesoporous silica and Al-SBA-15 periodic mesoporous aluminosilica, having comparable structural characteristics to the former material, have been compared. Raman spectroscopy shows that the any structural alteration of the Al-doped SBA-15 periodic mesoporous silica is due to the hydrothermal treatment. Our results show that the photoluminescence spectroscopic features at photon energies ranging from ~2.2 to 2.4 eV are shifted in Al-doped SBA-15 relative to that of Al-SBA-15 periodic mesoporous aluminosilica material.

Page 30

Photovoltaic properties of electrochemically deposited Cu2O/ZnO heterojunctions

Mingwei Shang1, 2 and Lifeng Dong2* 1 College of Materials Science and Engineering, Qingdao University of Science and

Technology, Qingdao 266042, China 2 Department of Physics, Astronomy and Materials Science, Missouri State University,

MO 65897, USA, LifengDong@MissouriState.edu Single-crystal n-type zinc oxide (ZnO) nanorod arrays and p-type cuprous oxide (Cu2O) thin film were deposited on FTO glass substrates by electrochemical deposition method using an electrochemical workstation. Scanning electron microscopy (SEM), X-ray energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) were used to study morphology, elemental concentration and distribution, and crystal structures of Cu2O/ZnO heterostructures. Experimental results demonstrate that the diameter of ZnO nanorods increased with the increase of the concentration of ZnCl2 precursor during the ZnO nanorod deposition, and electrical measurements confirm the formation of a p-n junction between Cu2O film and ZnO nanorods, which can efficiently facilitate the separation and transport of charge carriers at the Cu2O/ZnO interfaces for applications in solar cells. However, solution corrosion occurred during the Cu2O deposition and resulted in the conversion of some ZnO nanorods into nanotubes and thereby degraded their photovoltaic properties.

Page 31

Investigation of Superparamagnetism & Magnetocaloric effect in FeAs@C Core-Shell

Nanoparticles Prachi Desai1, Akshay Pariti2, Manashi Nath1

1Department of chemistry, Missouri S&T,Rolla,MO 65409 (nathm@mst.edu) 2Department of chemical engineering and Biochemical engineering, MissouriS&T ,

Rolla, MO 65409 Recently iron pnictide based compounds have been under immense scrutiny owing to discovery of superconductivity in the doped LnFeAsO (1111) and the AFeAs (A = alkali metal) series. The iron pnictide layer is believed to be responsible for superconductivity in these compounds. Iron pnictide is helimagnetic with magnetic moments being spiral w.r.t. the common c axis. Reports on nanostructured FeAs are rare and an in depth understanding of its properties is needed. We have developed a one-pot soft chemical method using a novel precursor Triphenylarsine (TPA) to synthesize monodisperse iron arsenide nanoparticles with a carbonaceous shell. Interestingly, this nanostructuring of FeAs@C nanoparticles brought about a change in magnetic properties in this system in comparison to the bulk. These were found to be superparamagnetic as revealed by magnetic characterization and the anhysteretic nature of the M vs H curves above the blocking temperature (5K-350K). As expected the blocking temperature (TB) varied with the magnetic field applied. The highest TB achieved was 240 K. Below TB, a narrow hysteresis curve suggested a magnetic ordering with a Hc value of 347 Oe. The high TB is of huge importance in applications related to magnetic storage media. This binary iron pnictide can be utilized as sacrificial template to synthesize nanostructured morphologies of these superconductors. Other potential applications of this binary pnictide system includes doping Fe with Co to yield (Fe,Co)As which exhibits magnetocaloric effect. Evaluation of magnetocaloric effect in the as synthesised FeAs@C nanoparticles will be potentially very interesting. Results encompassing, detailed characterization, magnetic studies, and magnetocaloric effect of FeAs nanoparticles, nanowires and [111] nanostructures will be presented. .

Page 32

Low temperature hydrocarbon-free growth of carbon nanotubes and filled nanofibers by chemical vapor transport

Wipula P. R. Liyanage, Manashi Nath Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409

Email: nathm@mst.edu

Abstract – The field of nanoscience continues exploration of suitable parameters for the production of carbon nanotubes for different applications. Requirement of high temperature and the use of gaseous hydrocarbons are some of the drawbacks identified in the current synthetic methods. The present study propose a gaseous hydrocarbon free approach for the synthesis of graphitic carbon nanotubes and filled nanofibers by chemical vapor deposition (CVD) technique using carbon rich transition metal precursors. This method entails thermal decomposition of iron acetylacetonate [Fe(acac)3] at low temperatures such as 180oC under nitrogen atmosphere to synthesize carbon nanotubes in the presence of palladium catalysts at 800oC in the same CVD apparatus. Characterization of the reaction product by scanning electron microscopy revealed a significant yield of uniform carbon nanotubes and nanofibers which are in the range of 90 – 120 nm in diameter and over 40µm in length (Figure 1). Investigation towards the synthesis of filled nanotubes and nanofibers indicated the possibility of synthesizing carbon nanotubes containing core-shell type nanostructures which provide a path to the synthesis of hybrid nanocomposites.

Figure 1: SEM image showing the yield of carbon nanotubes

Page 33

Patterned growth of vertically ordered nanotube arrays

Wipula P. R. Liyanage, Manashi Nath*

Department of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409 *Email: nathm@mst.edu

Abstract – Low dimensional semiconducting nanomaterials demonstrate remarkable properties in optical and nanoscale electronics applications due to their large surface area and quantum confinement effect1. A significant challenge faced in the development of nanomaterial incorporated devices is how to precisely control the shape, size, arrangement and location of the interesting nanostructures on the desired substrates. We report a method for fabricating semiconducting nanotube arrays with a high degree of precision over dimensions and distribution density, and exemplify the success of the protocol by growing CdTe and FeSe nanotube arrays respectively. This approach utilizes electron beam lithography to define the desired patterns over ITO coated glass (the conducting substrate) followed by electrodeposition on the lithographically patterned nanoelectrodes, for the growth of nanotubes (Figure 1). Scanning Electron Micrographs revealed that as-grown nanotubes consists of uniformly distributed nanotube arrays and it was also seen that this method can be scaled up to the precise production of nanotube arrays over a significantly larger area of the substrate which in turn make this method appropriate for fabrication of potential electronic device applications which utilize semiconducting and superconducting nanotube arrays.

Reference [1] P. Yang et al., Chem. Eur. J. 2002, 8, pp1260,1268

Figure 1: SEM image showing top-view of the patterned growth of nanotube arrays.

Page 34

Si-SiO2-Graphene Surface Merab Basiliaia1, Chris Ward1, Michael Giffin1, and Serif Uran1

1Pittsburg State University, Department of Physics, Pittsburg, KS 66762 (suran@pittstate.edu)

As the material aspect of graphene sheets are perfected, the application of it is also taking shape slowly. Energy storage [1] (supercapacitors, lithium ion batteries, solar cells), and composite materials that incorporate graphene are already being built and studied extensively. Silicon and graphene interaction appears to be important in understanding the nature of anode of lithium ion batteries. I will present some of our findings on this issue.

References [1] D. Wei et al, “Ultrathin Rechargable All-Solid-State Batteries Based on Monolayer

Graphene”, Journal of Materials Chemistry A, 1, 3177-3181 (2013). [2] K.J. Tielrooij et al, ”Photonexcitation cascade and multiple hot carrier generation in

graphene”, Nature Physics, 9, 248-252 (2013).

Page 35

Fabrication and characterization of CdS/MWNT/n-Si Transistor

Muatez Mohammed 1,4, Zhongrui Li 3, Johnathan Armstrong1,4 , Tar-pin Chen2,4, Jingbiao Cui2,4

Department of Applied Sciences1, Department of Physics and Astronomy2, University of Arkansas at Little Rock, GREEN Solar cell Research Center 4, Little Rock, AR 72204,

College of Engineering3, Florida State University, Tallahassee, FL 32310 Abstract:

A new type of n-p-n transistor photovoltaic devices based on CdS/MWNTs/n-Si configuration was fabricated by using a facile process. CdS quantum dots were deposit on fluorine-doped tin-oxide (FTO) glass using chemical bath deposition method. The MWNT (multi-wall carbon nanotube) film was coated on an n-type Si substrate by airbrushing technique. Then the CdS-coated FTO glass and the MWNT thin film fabricated on n-Si substrate were placed together to form an n-p-n transistor solar cell. The materials used for the n-p-n transistor solar cells were characterized by multiple techniques such as TGA, XRD, SEM, EDX, Raman, UV and I-V characteristic measurements.

The CdS layer acts as an n-type material for the transistor solar cells. Different CdS film thickness provides different photovoltaic response. The thickness of CdS film can be controlled by controlling the chemical bath deposition time. TGA (weight lost as a function of temperature) indicated that the purity of our MWNT is better than 99.7%. The XRD diffraction pattern of CdS thin film displays four diffraction peaks corresponding to the (100), (002), (110) and (112) crystalline planes for hexagonal structure indicating that CdS thin film has high crystallinity. SEM measurements show that the MWNTs form a randomly distributed network on the Si substrate while the surface of CdS is rough. EDS (energy dispersive x-ray spectroscopy) spectrum of CdS films indicates clearly that the specimen contains mostly cadmium (Cd) and sulfur (S).

Raman spectroscopic measurements on CdS/MWCT indicates that MWNTs exhibit several characteristic Raman peaks, such as a D-mode peaked at 1300-1335 cm-1, a G-mode peaked at 1510-1600 cm-1, and a 2D mode peaked at 2500-2750 cm–1. Raman spectrum recorded from 190 cm−1 to 1145 cm−1 for the CdS thin films shows three pronounce peaks. The peak at 300 cm-1 is from one phonon process, the broader peak shows at 525 cm−1 resulted from a two phonon process, while the broadest peak at 925 cm-1 results from a three phonon process. The Photoluminescence of a MWNTs thin film exhibits a main peak at approximately 530 nm (2.31 eV). PL spectrum of CdS thin film shows two peaks: the first one at ~ 435 nm is caused by the electrons at the luminescence band edge, and the second one at ~ 460 nm, which is ascribed to the recombination states of defects at the thin film of CdS. The UV transmission spectra of n-type CdS thin films show strong absorption between 300 – 600 nm. The absorption increases with increasing CdS thickness. I-V characteristic measurements show both short circuits current and open circuit voltage is very low if only MWNTs or CdS was used. The efficiency increases when both MWNTs and CdS thin films are used in the device to form an n-p-n transistor solar cell.

Page 36

A Novel Approach to Josephson Junctions: In Situ Atomic Layer Deposition

Alan J. Elliot1, Chunrui Ma1, Melisa Xin1, Rongtao Lu1, Siyuan Han1, Judy Z. Wu1.

1Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045 (contact alane@ku.edu)

Ultrathin dielectric tunneling barriers are critical to Josephson junction (JJ) based superconducting quantum bits (qubits). However, the prevailing technique of thermally oxidizing aluminum produces problematic defects, such as oxygen vacancies, which are believed to contribute to the decoherence of the qubits [1]. Development of alternative approaches for improved tunneling barriers is imperative. Atomic layer deposition (ALD) of aluminum oxide (Al2O3) is a promising alternative to resolve the issue of oxygen vacancies in the Al2O3 tunneling barrier, and its self-limiting growth mechanism provides atomic-scale precision in tunneling barrier thickness control [2]. ALD has been implemented in a high-vacuum sputtering system for in situ deposition of AL2O3 tunneling barriers. Josephson junctions were fabricated from Nb/Al2O3/Nb trilayers. In preliminary low temperature current-voltage measurements, the IcRn product was much smaller than expected from the Ambegaokar-Baratoff formula, suggesting a pair-breaking mechanism at the terminal ALD surface. Also, Ex Situ ellipsometry suggests significant thermal oxidation prior to the ALD process. In Situ plasma treatments were applied to the trilayers directly before and after the ALD process to address these issues. Current-voltage relationships were obtained for Josephson junctions with thermally oxidized, ALD, and plasma-treated ALD tunneling barriers to study the pair-breaking mechanism and to make ALD a competitive process for JJ based qubits. References [1] R. McDermott, “Materials origins of decoherence in superconducting Qubits”, IEEE Trans.

Appl. Supercond. 19, pp.2-13 (2009). [2] S.M. George, “Atomic Layer Deposition: An Overview”, Chem. Rev. 110, 111 (2010).

Page 37

Atomically Thin Layer MoSe2 on hBN Heterostructure Field-Effect Transistors with Large Photoresponse

Matthew Z. Bellus1, David L. Sicilian1, Hui-Chun Chien1, Benjamin I. Weintrub1, Jatinder Kumar1, A. Davis St. Aubin1, T. B. Hoffman2, Y.

Zhang2, and J. H. Edgar2, and Hsin-Ying Chiu1,*

1Department of Physics and Astronomy, University of Kansas, 2Department of Chemical Engineering, Kansas State University, *e-mail: chiu@ku.edu

Van der Waals heterostructures have recently attracted a lot of attention due to their potential wide range of applications in electronics and optoelectronics [1]. In this study, novel field effect transistors (FETs) were fabricated using atomically thin layer molybdenum diselenide (MoSe2), mechanically exfoliated and placed on hexagonal boron nitride (hBN). Under darkness, our FETs showed n-type doping and strong gate modulation yielding IOn/IOff ratios larger than 107, one order of magnitude larger than previous reports2. Using a two-probe measurement we report a likely underestimated room temperature mobility of ~27cm2/Vs. Under illumination these devices showed a strong photoresponse, thought to be the persistent photoconductive (PPC) effect [2], observed by relatively large currents with very little gate dependence. A ratio of the photoconductive “On” state with light to the “Off” state in dark, of greater than 105, is reported from solely light interaction. These results show promising optoelectronic characteristics in MoSe2 devices suitable for applications in photovoltaics, photosensors, and optoelectronics research.

References [1] A. K. Geim and I. V. Grigorieva, “Van der Waals heterostructures”, Nature 499, 419–425

(2013).

[2] S. Larentis et al, “Field-effect transistors and intrinsic mobility in ultra-thin MoSe2 layers”, Appl. Phys. Lett. 101, 223104 (2012).

[3] Y.C. Lee et al, ”Observation of persistent photoconductivity in 2H‐MoSe2 layered semiconductors”, J. Appl. Phys. 99, 063706 (2006).

Page 38

Investigation of Interfacial Interaction between Graphene and MoS2 by Raman Spectroscopy

Hui-Chun Chien, Matthew Z. Bellus, A. Davis St. Aubin, Jatinder Kumar, David L. Sicilian, and Hsin-Ying Chiu*

Department of Physics and Astronomy, University of Kansas, *e-mail: chiu@ku.edu

Van der Waals heterostructures have great potential for development in electronics and optoelectronics. Therefore, the interfacial interaction is a critical topic in the study of heterostructures. In this work, we employed Raman spectroscopy to study the interfacial interaction between graphene and MoS2. Gate-induced carrier density modulation in graphene can change the Raman spectrum in atomically thin layers of MoS2 via both the electron-phonon and interfacial interactions. The charge transfer between graphene and MoS2 is observed. Further investigation of the response of gate-induced interfacial interaction in this heterostructure will be presented. This study will pave the way for understanding the interfacial interaction with active control in graphene-based heterostructure devices.

Page 39

Excitonic dynamics in monolayer WSe2

Qiannan Cui, Frank Ceballos, Nardeep Kumar, and Hui Zhao*

Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA

* Corresponding author: huizhao@ku.edu

Recently, there is a growing interest in exploring two-dimensional crystals based on layered

materials. Although most efforts in recent years have been focused on graphene, other types of atomically thin layers have been successfully fabricated. Understanding their properties is important for exploring them for various applications. Furthermore, it is possible to make new

two-dimensional structures, the so-called van der Waals crystals, by stacking different types of atomic layers with the van der Waals force. In this regard, it is necessary to have a large number

of atomically thin materials available, with known properties.

Here we report an experimental study on a relatively less investigated two-dimensional crystal, monolayer WSe2, at room temperature by transient absorption microscopy [1]. In the experiment,

charge carriers are injected by interband absorption of a 405-nm femtosecond laser pulse. These carriers are expected to form excitons rapidly, which are stable at room temperature d ue to the

large exciton binding energy of this two-dimensional system. The dynamics of these excitons are studied by measuring the differential reflection of a time-delayed and spatially scanned 750-nm femtosecond laser pulse. By measuring the differential reflection signal as a function of the

pump power and probe wavelength, we find that the signal originates from absorption saturation induced by the excitons. By studying the spatiotemporal dynamics of these excitons, we deduced

energy relation rate, lifetime, and diffusion coefficient of excitons. For comparison, we also measured these parameters in a bulk crystal of WSe2.

References

[1] Brian A. Ruzicka, Rui Wang, Jessica Lohrman, Shenqiang Ren, and Hui Zhao, Exciton diffusion in semiconducting single-walled carbon nanotubes studied by transient absorption microscopy, Physical Review B, 86, 205417 (2012).

Page 40

Vertical Field-Effect Transistor Based on Graphene-MoS2 Heterostructures

Jatinder Kumar1, Hui-Chun Chien1, Matthew Z. Bellus1, David L. Sicilian1, Benjamin I. Weintrub1, A. Davis St. Aubin, T. B. Hoffman2, Y.

Zhang2, and J. H. Edgar2 and Hsin-Ying Chiu1 1Department of Physics and Astronomy, University of Kansas, 2Department of Chemical

Engineering, Kansas State University, *e-mail: chiu@ku.edu The remarkable properties of graphene have opened up the way for materials just one atom thick to be used in transistors [1]. It has created the possibility to form stable, single and few atomically thin layers of van der Waals materials for future advances in electronics and optoelectronics. An important development was the creation of heterostructures based on graphene and other two-dimensional crystals, which can be assembled into three-dimensional stacks with atomic layer precision [2]. Here, new field-effect transistor is fabricated where two-dimensional molybdenum disulphide is on top of graphene and carriers are transported vertically. The charge trapping characteristics of MoS2 and graphene in multi-stacked MoS2/graphene/hBN has been investigated. These devices exhibit response to the light and can be potentially used in light sensing devices.

References [1] Novoselov, K.S. et al. Two-dimensional atomic crystals. Proc. Natl Acad. Sci. USA 102,

10451-10453 (2005). [2] Dean, C.R. et al. Boron nitride substrates for high-quality graphene electronics. Nature

Nanotech. 5, 722-726 (2010).

Page 41

Dynamics of excitons in monolayer and bulk MoSe2 studied by transient absorption microscopy

Nardeep Kumar and Hui Zhao* Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045,

USA * Corresponding author: huizhao@ku.edu

Layered materials consist of planar, two-dimensional molecular layers stacked together by weak interlayer Van der Waals interactions with strong interatomic chemical bonds. Atomically thin molybdenum diselenide (MoSe2) is emerging as a new two-dimensional material with novel mechanical, electrical, and optical properties. We studied spatiotemporal dynamics of excitons in MoSe2 monolayer and bulk by using transient absorption microscopy [1,2]. Excitons are injected by using a femtosecond pulse pulse, and are detected by measuring differential reflection of a probe pulse. We observed exciton-induced absorption saturation, exciton-exciton annihilation, exciton diffusion, and exciton recombination in both monolayers and bulk crystals at room temoerature.

References [1] Nardeep Kumar, Jiaqi He, Dawei He, Yongsheng Wang, and Hui Zhao, Charge carrier dynamics in

bulk MoS2 crystal studied by transient absorption microscopy, Journal of Applied Physics, 113, 133702 (2013).

[2] Rui Wang, Brian A. Ruzicka, Nardeep Kumar, Matthew Z. Bellus, Hsin-Ying Chiu, and Hui Zhao, Ultrafast and spatially resolved studies of charge carriers in atomically-thin molybdenum disulfide, Physical Review B, 86, 045406 (2012).

Page 42

Graphene-based hybrid structure for transparent conductive electrodes

Jianwei Liu1, Rongtao Lu1, Guowei Xu1, Judy Wu1, Rongqing Hui2 1Department of Physics and Astronomy, University of Kansas

2Department of Electrical Engineering & Computer Science, University of Kansas Email: liuw@ku.edu, jwu@ku.edu

Graphene [1-3] based hybrid nanostrucures have been fabricated by various strategies for the application of transparent conductive electrodes. Using nanoimprint lithography, graphene nanohole arrays were fabricated to improve optical transmittacne due to the reduced surface coverage of graphene from nanoholes.Importantly, the exposed edges of the nanoholes provided effective sites for chemical doping using thionyl chloride was shown to enhance the conductance by a factor of 15-18 in contrast to only 2-4 for unpatterned graphene.[4] Also, using thermally assisted self-assembly, silver nanoparticles were deposited on graphene. The localized-surface-plasmonic effect is demonstrated with the resonance frequency shifting from 446 nm to 495 nm when the lateral dimension of the Ag nanoparticles increases from about 50 nm to 150 nm. The plasmonic graphene shows much improved electrical conductance by a factor of 2-4 as compared to the original graphene, making the plasmonic graphene a promising advanced transparent conductor with enhanced light scattering for thin-film optoelectronic devices.[5] Along this direction, a novel seedless floating growth process in solution has been developed to synthesize vertically alligned ZnO nanowire array on single-layer graphene sheets made in chemical vapor deposition. These 3D ZnO/graphene hybrid nanostructures provide an ideal template for UV detectors due to the superior wavelength selectivity and charge mobility.[6] Considering this seedless solution process can be carried out in air at a low temperature, it has a promising potential for low-cost commercialization of ZnO/graphene hybrids at low costs for various applications of photodetectors, photovoltaics, photocatalysis, sensors, and other optoelectronic devices.

References [1] K.S. Novoselov et al, “Electric field effect in atomically thin carbon films”, Science 306, 666 (2004). [2] A.K. Gein et al, “The rise of graphene”, Nature Materials 6, 183 (2007). [3] X.S. Li et al, “Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper

Foils” Science, 324, 1312 (2009). [4] J.W. Liu et al, “Doped graphene nanohole arrays for flexible transparent conductors”, Applied

Physics Letters 99, 023111 (2011). [5] G.W. Xu et al, “Plasmonic Graphene Transparent Conductors”, Advanced Materials 24,

OP071 (2012). [6] J.W. Liu et al, “Development of a Seedless Floating Growth Process in Solution for Synthesis

of Crystalline ZnO Micro/Nanowire Arrays on Graphene: Towards High-Performance Nanohybrid Ultraviolet Photodetectors” Advanced Functional Materials, DOI: 10.1002/adfm.201300468 (2013).

Page 43

In-situ Fabrication of Plasmonic Gold Nanoparticles on Graphene for Surface Enhanced Raman Spectroscopy

Rongtao Lu, Jianwei Liu and Judy Z. Wu Department of Physics & Astronomy, University of Kansas, Lawrence, KS 66045

Email: rtlu@ku.edu, jwu@ku.edu Graphene has been used as substrate of surface enhanced Raman spectroscopy (SERS) [1], and further explorations confirmed giant SERS improvements by applying plasmonic graphene structure with metal nanoparticles [2]. Most previous plasmonic nanostructure fabrications on graphene employed ex-situ annealing or other colloidal methods; the necessary high temperature processing limits the plasmonic structure development and affected the performance of graphene, and interface contact issue of colloidal method degrades the surface plasmonic effect. We have developed an in-situ strategy of fabricating gold nanoparticles by in-situ evaporating gold film onto heated substrates and preliminary experiments confirmed the plasmonic effect. Gold nanoparticles with different dimensions were obtained by controlling the nominal thickness of gold film from 2 nm to 12 nm. Scanning electron microscopy (SEM) clearly showed the separation of these gold nanoparticles. Optical transmission characterizations confirm the plasmonic effect with tunable resonance wavelengths. More systematic SERS measurements on organic samples are ongoing.

References 1. X. Ling, L. M. Xie, Y. Fang, H. Xu, H. L. Zhang, J. Kong, M. S. Dresselhaus, J. Zhang and Z. F. Liu,"Can Graphene be used as a Substrate for Raman Enhancement?", Nano Lett. 10, 553 (2010). 2. W. G. Xu, N. N. Mao and J. Zhang,"Graphene: A Platform for Surface-Enhanced Raman Spectroscopy", Small 9, 1206 (2013).

Page 44

Highly Epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 Thin Films for Energy Application

Chunrui Ma1, Beihai Ma2, Shaobo Mi3, Chunlin Jia3 and Judy Wu1

1 Department of Physics and Astronomy, university of Kansas, Lawrence, Kansas, 66045, USA(chunrui.ma@gmail.com and jwu@ku.edu )

2 Energy Systems Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 3 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for

Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China

With the needs for development of sustainable energy technologies, devices for

effectively absorbing, converting, storing, and supplying electrical energy are in increasing demand. Not only high energy storage density but also high-power output is required for many applications. Commercial electrical energy storage and supply devices include fuel cells, batteries, electro-chemical supercapacitors, and dielectric capacitors. Among them, fuel cells and batteries exhibit high energy density, but relatively low power density because of the slow movement of charge carriers. Electrochemical supercapacitors offer improved power density at moderate energy density and are promising for many power system applications, but their charge and/or discharge process still requires seconds or tens of seconds. In contrast, dielectric capacitors provide the highest power density because of their extremely high charge/discharge speed. This characteristic makes dielectric capacitors well suited to energy storage applications when high power delivery or uptake is required. However, traditional dielectric capacitors possess low energy density (≤0.1 J/cm3). Recently, polymer ferroelectrics, ceramic ferroelectrics, antiferroelectrics, and relaxor ferroelectrics have shown better potential and higher energy density than linear dielectrics [1-3]. Lead lanthanum zirconate titanate (PLZT(8/52/48)) grown on metal foils showed energy density of ≈53 J/cm3 [4-5]. By far, the vast majority of ceramic dielectric films are nontextured polycrystalline films fabricated on silicon or platinized silicon wafers [6-8]. Epitaxial film can exhibit unique properties that are desirable for particular applications. Thus we fabricated the highly epitaxial PLZT (8/52/48) /LaNiO3 (LNO) heterostructures were on (001) LaAlO3 substrate by using a KrF excimer pulsed laser deposition system with a wavelength of 248 nm and a 10 Hz repetition rate and investigated the physical properties of the film, which indicated that the film has a great potential for the energy application. References

1. B. Chu, X. Zhou, K. Ren, B. Neese, M. Lin, Q. Wang, F. Bauer, and Q. M.

Zhang, Science 313 (2006) 334. 2. K. Yao, S. Chen, M. Rahimabady, M. S. Mirshekarloo, S. Yu, F. E. H. Toy, T.

Sritharan, and L. Lu, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58 (2011) 1968.

3. X. Hao, Y. Wang, J. Yang, S. An, and J. Xu, J. Appl. Phys. 112 (2012) 114111.

Page 45

4. B. Ma, D. K. Kwon, M. Narayanan, U. Balachandran, Mater. Res. Bull. 44 (2009) 11.

5. B. Ma, D. K. Kwon, M. Narayanan, U. Balachandran, J. Mater. Res. 24 (2009) 2993.

6. H.-J. Zhao, T.-L. Ren, N.-X. Zhang, R.-Z. Zuo, X.-H. Wang, L.-T. Liu, Z.-J. Li, Z.-L. Gui, and L.-T. Li, Mater. Sci. Eng. B 99 (2003) 195.

7. G.L. Brennecka and B.A. Tuttle, J. Mater. Res. 22 (2007) 2868. 8. P. Verardi, F. Craciun, N. Scarisoreanu, G. Epurescu, M. Dinescu, I. Vrejoiu,

A. Dauscher, Appl. Phys. A, 79 (2004) 1283.

Page 46

Conformal coating of vertically aligned carbon nanofiber arrays via atomic layer deposition

Gary Malek1, Emery Brown2, Steven Klankowski2, Jianwei Liu1, Alan Elliot1, Rongtao Lu1, Jun Li2 and Judy Wu1

1Department of Physics and Astronomy, University of Kansas 2Department of Chemistry, Kansas State University

Email: gmalek@ku.edu, jwu@ku.edu Vertically aligned carbon nanofiber (VACNF) arrays [1] were utilized as high-aspect-ratio, conducting substrates for fabrication of core-shell structures. Conformal coatings of aluminum oxide (Al2O3) [2] and Al-doped zinc oxide (AZO) [3] were accomplished via atomic layer deposition (ALD), which utilizes a self-terminating growth mechanism to provide extremely accurate thickness control. The unique advantage in utilizing carbon nanofibers (CNFs) instead of carbon nanotubes (CNTs) was due to the presence of highly reactive dangling bonds along the sidewalls. These dangling bonds eliminated the need for nitrogen dioxide pre-functionalization as is necessary when coating CNTs via ALD [4]. Instead, the ALD sequencing began with a simple water exposure, which prepared the surfaces of the CNFs with hydroxyl groups that reacted easily with the Al precursor. The resulting core-shell structure, consisting of the VACNFs enclosed in 20 nm Al2O3 surrounded by 30 nm AZO, was verified by high-resolution transmission electron microscopy as well as field emission scanning electron microscopy. A preliminary planar capacitor fabricated with a 20 nm ALD Al2O3 dielectric layer achieved specific capacitances from 262 nF/cm2 at 1000 V/s up to 526 nF/cm2 at 25 mV/s. The breakdown electric field for this capacitor was determined to be 1.4 MV/cm [5]. Additional testing was also performed utilizing hafnium oxide as the dielectric layer. These promising results reveal that conformally coated VACNF arrays via ALD may ultimately provide a possible solid-state supercapacitor design.

References [1] J. Li et al, “Electronic properties of multiwalled carbon nanotubes in an embedded vertical

array”, Applied Physics Letters 81, 5 (2002). [2] J.W. Elam et al. “Viscous flow reactor with quartz crystal microbalance for thin film growth

by atomic layer deposition”, Review of Scientific Instruments 73, 8 (2002). [3] J.W. Elam et al. “Properties of ZnO/Al2O3 Alloy Films Grown Using Atomic Layer

Deposition Techniques”, Journal of The Electrochemical Society 150, 6 (2003). [4] D. B. Farmer et al. “Atomic Layer Deposition on Suspended Single-Walled Carbon

Nanotubes via Gas-Phase Noncovalent Functionalization”, Nano Letters 6, 4 (2006). [5] G. Malek et al, unpublished.

Page 47

Pulsed Laser Deposition of Thin Film CdTe/CdS Solar Cells with CdS/ZnS Superlattice Windows

Jake Meeth1, Paul Harrison1, Jianwei Liu1, Bing Li2, Rongtao Lu1, Lianghuan

Feng2, Judy Wu1 1Department of Physics and Astronomy, Lawrence, KS, 66046, USA

2College of Materials Science and Engineering, Sichuan University, Chengdu 610064, China Pulsed Laser Deposition (PLD) is advantageous to the fabrication of superlattice structures and was applied to generate CdS(3nm)/ZnS(2nm) and CdS(6nm)/ZnS(4nm) superlattices within the CdS window layers of thin film CdTe/CdS solar cells to explore ways to improve the microstructure and transmittance of the window layer. At the same window layer thickness, the composite windows made with CdS/ZnS superlattices sandwiched with CdS layers have higher transmittance as compared to the single layer window of CdS. This resulted in enhanced short circuit current in the CdTe solar cells with the composite window as expected. Power conversion efficiency up to 5.2% has been obtained in CdTe (1.5 µm) using this composite window. With optimization of the processing conditions, this composite window structure may provide a scheme to modify the window for better power-conversion efficiency in thin film CdTe solar cells.

Page 48

Assembling Heterostructures with Clean Interfaces between hBN and Other van der Waals Materials

David L. Sicilian1,*, Benjamin I. Weintrub1,*, Hui-Chun Chien1, Jatinder Kumar1, Matthew Z. Bellus1, A. Davis St. Aubin1, T. B. Hoffman2, Y. Zhang2,

and J. H. Edgar2 and Hsin-Ying Chiu1,# 1Department of Physics and Astronomy, University of Kansas, 2Department of Chemical

Engineering, Kansas State University, #e-mail: chiu@ku.edu

The discovery of graphene and other two-dimensional materials has caused an explosion of research due to their unique properties and their potential as semiconductor materials. It has also been shown that it is possible to stack two-dimensional materials together, creating multilayer heterostructures, and yielding yet another vast expanse of research possibilities [1]. Hexagonal Boron Nitride (hBN) became of particular interest when it was discovered that stacking it with graphene results in substantial improvement of graphene’s properties [2]. Even more exciting is the observation that graphene’s band structure is modified upon specific alignment of the hBN/graphene crystal lattice interface. It is believed that hBN will have a similar affect on other van der Waals materials. Although Graphene/hBN heterostructures have yielded exciting results, there seems to be a common problem with organic contaminants between layers [3]. These contaminants harm the quality of the heterostructures, affect the electrical properties, and prevent the heterostructures from having a true van der Waals interaction between surfaces [3]. Transmission electron microscopy has been used to discover that hydrocarbons are the contaminants that densely cover the surfaces in graphene/hBN heterostructures [3]. Scanning electron microscopy (SEM) offers a quick and effective tool for investigating the surface cleanliness of van der Waals materials. With SEM images we are able to see the cracks and crevices of an hBN crystal. We have also been able to see that the residue trapped between graphene and hBN surfaces will conglomerate and settle into these cracks. This leaves the rest of the interface without residue. Our SEM investigations have also been used optimize our cleaning and annealing procedure so that residue can be best reduced before assembly, and the heterostructure interfaces can be as clean as possible. Both SEM and AFM were used to investigate the effectiveness of different solvents and annealing parameters for creating the cleanest possible surfaces for the van der Waals materials, and therefore the cleanest interfaces in heterostructures. This work will pave the way for the assembly of heterostructures with purely van der walls forces between the layers of two-dimensional materials. *These authors contributed equally to this work.

References [1] A. K. Geim and I. V. Grigorieva, “Van der Waals heterostructures”, Nature 499, 419–425 (2013).

[2] Dean, C. R. et al. “Boron nitride substrates for high-quality graphene electronics”, Nature Nanotech. 5, 722–726 (2010).

[3] Haigh, S. J. et al. “Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices”, Nature Mater. 11, 764–767 (2012).

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Fabrication and Charactetization of InGaAs Metal-Oxide-Semiconductor Capacitors with HfO2 Dielectrics

Jill Wenderott1,*, Cheng-Ying Huang2, and Mark Rodwell2 1Department of Physics and Astronomy, University of Kansas, 2ECE, University

California Santa Barbara, *email: jillk@ku.edu

III-V indium gallium arsenide (InGaAs) metal-oxide-semiconductor field effect transistors (MOSFETs) are promising candidates for next-generation low power logic technology. A major challenge for III-V MOSFETs is the development of suitable gate dielectrics with low interface trap densities. This project focused on the fabrication of InGaAs metal-oxide-semiconductor capacitors with hafnium oxide (HfO2) dielectrics grown by atomic layer deposition (ALD). Several studies were conducted involving in-situ ALD surface cleaning, HfO2 growth temperature and post-deposition forming gas anneal parameters. The two types of surface cleaning investigated to reduce interface trap density were hydrogen plasma/trimethylaluminum (TMA) and nitrogen plasma/TMA. The post-deposition forming gas anneal was optimized by testing different ramp rates and annealing temperatures. The InGaAs MOSCaps were characterized using capacitance-voltage measurements, and the interface trap densities were evaluated using the conductance method.

Page 50

Classification of CSH Crystals via a Quantum Mechanical Metric

C. C. Dharmawardhana1, S. Aryal1, A. Misra2, W. Y. Ching1 1Department of Physics and Astronomy, University of Missouri – Kansas City, Kansas

City, MO 64110, USA (ccdxz8@mail.umkc.edu). 2Department of Civil, Environmental, and Architectural Engineering, University of

Kansas, Lawrence, KS 66045, USA. The Calcium Silicate Hydrates (CSH) is the main binding phase of concrete comprised a mired of crystalline mineral phases that are poorly ordered and vastly complex in composition. The traditional classifications metrics give little understanding of the chemical and mechanical behavior which calls for new strategy to understand the complex nature of the problem. This work is based on the idea of using the bond order density (BOD) in the crystal as a theoretical metric to classify this the CSH and related crystals with Ca/Si ranging from 0.67 to 3.00, in order to gain much needed insight on the structure of CSH gel [1].

We have carried out a series of detailed calculations on the mechanical and electronic structure properties of the following CSH crystals with different H2O and (OH) contnets: jennite [Ca9Si6O18(OH)6•8H2O], tobermorite-9Å [Ca5Si6O17•5H2O], tobermorite-11Å [Ca4Si6O15(OH)2•5H2O], tobermorite-14Å [Ca5Si6O16(OH)2•7H2O], afwillite [Ca3(SiO3OH)2•2H2O], α-C2SH [Ca2(HSiO4)(OH)], Killalaite [Ca6.4(H0.6Si2O7)2(OH)2], Suolunite [CaSiO2.5(OH)·0.5•H2O], Xonotlite [Ca6Si6O17(OH)2], Portlandite [Ca(OH)2], and the clinker phases alite [3CaO•SiO2] and belite [2CaO•SiO2]. This large data base of different CSH and related crystals enable us to correlate their mechanical properties with electronic structure properties to shed light on the general priciples governing the structure of the cements. References [1] Dharmawardhana, C.C., et al., Role of interatomic bonding in the mechanical anisotropy

and interlayer cohesion of CSH crystals. Cement and Concrete Research, 2013. 52(0): p. 123-130.

Page 51

Thermo-mechanical Properties of Mo5Si3 (T1 Phase)-based Alloys

C. C. Dharmawardhana,1 R. Sakidja,1 and W. Y. Ching1 1Department of Physics and Astronomy, University of Missouri – Kansas City, Kansas

City, Missouri 64110, USA (ccdxz8@mail.umkc.edu) As a possible candidate for the new generation of high temperature materials, Mo-Si class of alloys has become an attractive material for intense research. However, the T1 (Mo5Si3) phase has very high thermal expansion anisotropy (TEA) which adversely affects its strength and stability as a material for high temperature coating [1]. Alloying is traditionally used as a strategy to reduce the TEA. Mechanical properties at very high temperatures are difficult to address purely by experimental means and the current theoretical appraoches are also woefully inadequate. Here, we use ab-initio molecular dynamics (AIMD) to simulate the alloying behavior and obtain the coefficient of thermal expansion (CTE) and TEA [2]. We chose elements of V and Al for substitution at the Mo and Si sites respectively in Mo5Si3 with different range of compositions. Out of the two Mo sites (16K & 4B), we observe that V prefers the chain sites (4b) which results in the unusual anisotropy behaviour with alloy composition consistant with experimental observation. On the other hand, Al substituting Si shows normal behaviour. Our results indicate that Al to be much more effective in reducing the TEA of the T1 phase with with Al concentration at about 16.6% of the Si sites. Results on the temperate-dependent mechanical properties of these alloys will also be reported. References [1] Rawn, C.J., J.H. Schneibel, and C.L. Fu, Thermal expansion anisotropy and site

occupation of the pseudo-binary molybdenum vanadium silicide Mo5Si3–V5Si3. Acta Materialia, 2005. 53(8): p. 2431-2437.

[2] Dharmawardhana, C.C., et al., Temperature dependent mechanical properties of Mo-Si-B compounds via ab initio molecular dynamics. APL Materials, 2013. 1(1): p. 012106.

Page 52

A Neural Network Based Approach to Self-Consistent Field Calculations in ab initio Electronic Structure

Calculations Naseer Dari and Paul Rulis

Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110, USA (namc55@mail.umkc.edu)

Within the density functional theory (DFT) based ab initio orthogonalized linear combination of atomic orbitals (OLCAO) [1] method for electronic structure calculation the solid state electronic potential function is expressed as a summation of atom centered Gaussian functions. The coefficients of the terms of this function are normally determined through self-consistent field (SCF) iterations applied to the whole system. However, for complex systems with many atoms (e.g systems with defects or large biomolecules) the SCF calculation (or the preparation for it) becomes excessively expensive in terms of computation and time. A new approach to obtaining the potential function coefficients and subsequently computing the total energy has demonstrated encouraging results when applied to a passive defect model and a self-interstitial model of pure silicon. In this approach an artificial neural network (ANN) was used to determine the potential function based only on training data obtained from calculations of amorphous silicon. Through this approach it becomes possible to bypass the need for the SCF calculation if sufficient training data can be obtained from similar, but simpler, systems. Extension of this method to other materials will be discussed.

References [1] W.-Y. Ching and P. Rulis, Electronic Structure Methods for Complex Materials. Oxford

University Press, 2012.

Page 53

A Multi-method Approach to Modeling Amorphous Hydrogenated Boron Carbide

Rachel Cramm Horn, Anthony Caruso, Michelle Paquette, and Paul Rulis

University of Missouri – Kansas City, Department of Physics and Astronomy <rec44f@mail.umkc.edu>

Amorphous hydrogenated boron carbide (a-BxC:Hy) is a thin film with potential practical applications in solid state neutron detection and as a low-k dielectric in the semiconductor industry. It is also of fundamental interest because amorphous molecular solids are, in general, not well understood. Although the detailed atomic structure of a-BxC:Hy is not yet known, some information about the material’s composition and complex bonding rules has been determined. [1] Because a-BxC:Hy is an amorphous solid that also has some medium-range order, it presents substantial challenges to most traditional modeling techniques. This poster presents progress in the development of a multi-method modeling approach that uses the strengths of several different traditional approaches to offset those aspects of each approach that are ill-suited to this type of material.

The models presented were created using different combinations of classical molecular dynamics (MD), ab initio relaxation, and manual manipulation including (a) a “condensation scheme” wherein the various molecular components of a-BxC:Hy begin in positions far from one another and then the classical MD program LAMMPS [2] is used to decrease the size of their simulation box while the components move freely and bond together in an amorphous mass, (b) the condensation scheme followed by an ab initio relaxation using VASP, [3] and (c) the condensation scheme, beginning not with molecular components but with small hand-built “nanoclusters.”

References [1] M. Paquette et al, “The local physical structure of amorphous hydrogenated boron carbide:

insights from magic angle spinning solid-state NMR spectroscopy,” J. of Phys.: Cond. Mat. 23(43), 435002 (2011)

J. Smith et al, “Article title”, Phys. Rev. B 95, 456789 (2015). [2] S. Plimpton, ”Fast parallel algorithms for short-range molecular dynamics,” J. Of Comp.

Phys. 117, 1-19 (1995). [3] G. Kresse et al, ”Efficient iterative schemes for ab intio total-energy calculations using a

plane-wave basis set,” Phys. Rev. B 54(16), 11169 (1996).

Page 54

Computational Study of a Model of Type I Collagen and Implementation of an Amino Acid Potential Method

Applicable to Large Proteins Jay Eifler1, Paul Rulis1, Rex Tai2, and W.Y. Ching2

1Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA (jqewt2@mail.umkc.edu)

2Weinberg School of Arts and Sciences, Northwestern University, Evanston, IL 60201,

USA We have developed a simplified approach for calculating electronic structure properties of large proteins using the density functional theory (DFT)-based orthogonalized linear combination of atomic orbitals (OLCAO) method. Since proteins are composed of a sequence of amino acids, we have created a database of amino-acid potentials using self-consistent field (SCF) calculations. The amino-acid potentials are then used in the calculations for the proteins. This enables us to skip the costly SCF calculation for the entire protein but still retain the ab initio level of results for the protein. We call it the amino acid potential method (AAPM). The method is applied to a collagen model consists of 90 amino-acids with a composition similar to natural collagen, or the 7-2 triple-helical structural model of type I collagen. To assess the accuracy of the AAPM results, the effective charge (Q*) on each atom from the amino-acid approach was compared to Q* from the full SCF calculation on the collagen model. Very close agreements are obtained validating the accuracy of AAPM with a much reduced computational cost. In addition to Q*, density of states (DOS) and bond order (ρ) values especially the H-bonding are also obtained.

We are currently extending the study to a much larger model for brome mosaic virus (BMV). The structure for the BMV model is obtained from the protein databank (pdb) 1JS9. No water molecules or other ions were included in the models, only dry forms with all charged groups in the neutral form are used.

Page 55

Mobility–Lifetime Product Measurement in Amorphous Hydrogenated Boron Carbide Using the Steady-State

Photoconductivity Method

Justin D. Hurley, Mahbube K. Siddiki, Christopher L. Keck, Bradley J. Nordell, Thuong D. Nguyen, Anthony N. Caruso, and Michelle M. Paquette

Department of Physics and Astronomy, University of Missouri – Kansas City, Kansas

City, MO 64110, jdh7dd@mail.umkc.edu

As a p-type high-band-gap (>2.5 eV), high-resistivity (>1012 Ω·cm) semiconductor, amorphous hydrogenated boron carbide (a-BxC:Hy) is one of a handful materials suitable for direct-conversion solid-state neutron detection. Traditionally, there has been minimal investigation into the boron carbide class of solids outside of its mechanical uses, and the basic knowledge of electrical transport properties needed to optimize a-BxC:Hy for detector applications is lacking. In particular, the mobility–lifetime product (μτ), a measure of the ability to extract and transport charges within a material, is an important figure of metric for detector devices. Herein we describe our implementation of the steady-state photoconductivity method for the determination of μτ in a-BxC:Hy films.

Page 56

Mobility Measurements of Amorphous Hydrogenated Boron Carbide

Utilizing the Dark-Injection Space-Charge-Limited Current Method #Christopher L. Keck,1

Bradley J. Nordell,1 Thuong D. Nguyen,1 Justin D. Hurley,1 A. N. Caruso,1 and Michelle M. Paquette1

1Department of Physics & Astronomy, University of Missouri-Kansas City, Kansas City, MO

64110, clk841@mail.umkc.edu Abstract: As a p-type semiconductor with a high cross-section for neutron capture, boron carbide is of

interest for solid-state direct-conversion neutron detection. There has been particular interest in thin-film

amorphous hydrogenated boron carbide (a-BxC:Hy) grown by plasma-enhanced chemical vapor

deposition (PECVD) from orthocarborane because it demonstrates atypically high resistivities (on the

order of 1012 Ω·cm), important for suppressing detector leakage current. Although some research

investigating this material for detection applications has been done, rigorous electrical carrier transport

studies are still needed if efficient devices are to be realized. The experimental determination and physical

interpretation of the material’s mobility is complicated by the fact that it is likely well below the range

measureable by a DC or AC Hall Effect system. To get around this limitation, we implemented a system

that utilizes the dark-injection space-charge-limited current (DI-SCLC) method. This contribution will

describe the theory behind the DI-SCLC method and how it can be utilized to determine a material’s

mobility. It will also cover how the system was built, as well as go over measurement results, their

meanings, and future experiments.

Page 57

Oxidation of Cr2AlC (0001): Insights from ab initio calculations

Neng Li, Ridwan Sakidja and Wai-Yim Ching Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City,

MO 64110,USA (Email:lineng@umkc.edu) We performed an investigation of the oxidation of the technologically relevant Cr2AlC (0001) surface by ab initio calculations. Although, the surface structure of Cr2AlC (0001) is already reported[1-2], the details of oxygen-(0001) surface interaction is still lacking. Such a study is needed not only the fundamental understanding oxidation and corresion of MAX Phases. In this work, four possible terminations Al-, Cr(C)-, C-, Cr(Al)- terminated Cr2AlC (0001) surface are considered. Full relaxations are performed for the four surface configurations without any symmetric constraint, and obtained the cleavage energy created by breaking the Cr-Al bonds in Cr2AlC with a vacuum region of 15 Å. The corresponding surface energies of the four configurations are computed and compared, which indicated that the Al- and Cr(C)-terminated surfaces are more stable than the C- and Cr(Al)-terminated surfaces. For the most stable Al-terminated Cr2AlC (0001) surface, a detailed model describing the oxygen-surface interactions is developed by exploring the adsorption energetics. Based on the evaluation of the energetics and the structural properties of the atomistic models generated, the results point to an initial stage of the Cr2AlC (0001) surface oxidation with some similarities with those observed in Al (111) layer [3]. Our findings on the bonding mechanism of single O and O2 molecular adsorption of the surface may lead to further alloying strategies to enhance oxidation resistance in a wide range of refractory-metal based MAX phases.

References [1] J. Wang et al, “Stable M2AlC(0001) surfaces (M = Ti, V and Cr) by first-principles

investigation”, J. Phys.: Condens. Matter 20, 225006 (2008). [2] Z. Sun et al, “Ab initio study of the Cr2AlC (0001) surface”, Appl. Phys. Lett. 88, 161913

(2006). [3] N. Li et al, “Oxidation of Cr2AlC (0001): Insights from ab initio calculations”, JOM (in

press).

Page 58

Crystal Structure and Elastic Properties of MAX-like (Cr2Hf)2Al3C3

Yuxiang Mo, Sitaram Aryal, Paul Rulis, and Wai-Yim Ching Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City,

Missouri 64110, USA (chingw@umkc.edu) “MAX phase” represents a class of layered ternary transition-metal carbides and nitrides that have a general formula: Mn+1AXn [M: an early transition-metal element, A: an A group (III, IV, V, or VI) element, X: carbon or nitrogen, and n = 1 to 3]. These materials are good conductors of heat and electricity. They are light-weight, stiff, and refractory, but also easily machinable. They can tolerate external damages and internal defects, as well as thermal shocks and high-temperature oxidation. This novel combination of properties have made MAX phases highly regarded candidates for various technological and engineering applications [1-5].

Using (Cr2Hf)2Al3C3 as an example, we demonstrate the possibility of incorporating more types of elements into a MAX phase while maintaining the crystallinity, instead of creating solid-solution phases. The crystal structure and elastic properties of MAX-like (Cr2Hf)2Al3C3 are studied using the Vienna Ab initio Simulation Package. Unlike MAX phases with a hexagonal symmetry (P63/mmc, #194), (Cr2Hf)2Al3C3 as a new type of crystalline material (named D-MAX phase) crystallizes in the monoclinic space group of P21/m (#11) with lattice parameters of a = 5.1739 Å, b = 5.1974 Å, c = 12.8019 Å; α = β = 90°, γ = 119.8509°. Its structure is found to be energetically favorable with an energy (per formula unit) of -102.13 eV, significantly lower than those of the allotropic segregation (-100.05 eV) and solid-solution (-100.13 eV) phases. Calculations using a stress vs. strain approach and the VRH approximation for polycrystals also show that (Cr2Hf)2Al3C3 has outstanding elastic moduli (bulk/shear/Young’s: 181.5/125.2/305.3 GPa) compared with those of the competing segregation (151.8/104.8/255.7 GPa) and solid-solution (148.9/89.0/222.7 GPa) phases.

References [1] Barsoum MW, “The MN+1AXN phases: a new class of solids; thermodynamically stable nanolaminates”, Prog. Solid State Chem. 28, 201 (2000). [2] J. Wang et al, “Recent Progress in Theoretical Prediction, Preparation, and Characterization of Layered Ternary Transition-Metal Carbides”, Annu. Rev. Mater. Res. 39, 415 (2009). [3] P. Eklund et al, “The Mn+1AXn phases: Materials science and thin-film processing”, Thin Solid Films 518, 1851 (2010). [4] J.C. Nappé et al, “Damages induced by heavy ions in titanium silicon carbide: Effects of nuclear and electronic interactions at room temperature”, J. Nucl. Mater. 385, 304 (2009). [5] F. Meng et al, “Synthesis of Ti3SiC2 by high energy ball milling and reactive sintering from Ti, Si, and C elements”, J. Nucl. Mater. 386, 647 (2009).

Page 59

Laser ablation of Ge in liquid in electric field Y. Li *, O.R. Musaev, J.M. Wrobel, and M.B. Kruger

Department Physics and Astronomy, UMKC ylnq9@mail.umkc.edu Laser ablation in liquids is a method of nanoparticle fabrication that is alternative to chemical methods. Intensive laser pulses convert a solid target into an overheated liquid that is in a metastable state, in which homogeneous nucleation occurs. A result is the formation of a foam of nanodroplets and vapor. The liquid environment that the target is immerse in plays the role of a collector of nanoparticles that eventually form a colloidal suspension. Though the properties of nanoparticles can be modified by selecting different pulse energies, wavelengths of radiation and liquids, more control of nanoparticle synthesis is desirable. In this work, laser ablation under different external electric fields was tried as a method of nanoparticle modification.

An XeF excimer laser was used to ablate Ge targets in static electric fields of different magnitudes with the targets immersed in either water or alcohol. The electric field magnitude was in the range from 0 to 1,000 V/cm. The ablated materials were imaged using a transmission electron microscope. It was observed that there was a decrease in the average particle size with increasing electric field strength for ablation in both liquids. This opens the interesting opportunity to control nanoparticle size by application of an electric field.

Page 60

Monitoring an Orthocarborane Plasma for Amorphous Hydrogenated Boron Carbide Film Growth using

Optical Emission spectroscopy Thuong D. Nguyen#1, Emeshaw Ashenafi2, Anthony N. Caruso1, and

Michelle M. Paquette1 1Department of Physics and Astronomy, University of Missouri-Kansas City, 5110

Rockhill Road, Kansas City, MO 64110. Email: tdnz72@mail.umkc.edu 2Department of Computer Science and Electrical Engineering, University of Missouri-

Kansas City, Kansas City, MO 64110 Amorphous hydrogenated boron carbide (C10B10H12) grown by plasma-enhanced chemical vapor deposition from orthocarborane (C2B10H12) is a semi-insulating material of interest for a number of specialized nano-electronic and semiconductor applications including low-k dielectrics and solid-state neutron detection. One of the steps in understanding and optimizing solid-state material properties is studying the thin-film growth process. Optical emission spectroscopy (OES), which detects emission lines from excited chemical species, is a non-invasive real-time tool for studying plasmas, useful for process monitoring (plasma uniformity, reproducibility, impurity detection, etc.), determining plasma parameters such as electron density and concentration, and identifying/monitoring reactive excited species within the plasma. Preliminary work toward monitoring an orthocarborane plasma by OES, including the effects of carrier/reactive gas (argon, methane, hydrogen), flow rates, pressure, power, etc, will be described.

Page 61

Controlling the dielectric and electronic properties of PECVD-grown amorphous hydrogenated boron carbide thin

films #Bradley J. Nordell1, Sudarshan Karki1, Thuong D. Nyuyen1, C. Keck1, Sean W

King2, Sudaunshu Purohit3, A. N. Caruso,1 and Michelle M. Paquette1 1Department of Physics and Astronomy, University of Missouri-Kansas City, 5110 Rockhill

Road, Kansas City, MO 64110. Email: bjn279@mail.umkc.edu. 2Logic Technology Development, Intel Corporation, Hilsboro, OR.

3Department of Chemistry University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110

Thin-film amorphous hydrogenated boron carbide (a-BxC:Hy), grown by plasma-enhanced chemical vapor deposition (PECVD) from orthocarborane (C2B10H12) has emerged as a promising semi-insulating, moderately high bandgap (2–4 eV), p-type material for direct-conversion solid-state neutron detector and low-dielectric-constant (low-κ) intra/interlayer dielectric (ILD) applications. As of present day, there is a deficit in phenomenological understanding of dielectric, optical, electronic, and charge transport properties of amorphous materials in general, and a-BxC:Hy in particular. In this study, various types of spectroscopic (ellipsometry, UVVis, and FTIR) and electrical (capacitance–voltage and current–voltage) characterization techniques in the low (100 kHz), medium (300 GHz–400 THz), and high (1000 THz) frequency/energy range were used to determine the dielectric, optical, and electrical properties. The origin and optimization of the dielectric properties (both real and imaginary parts) of a-BxC:Hy will be examined. Moreover, it will be shown that the dielectric properties are a useful method in probing the electronic (e.g., density of states), optical, and chemical properties of amorphous materials. More specifically, the phenomenological effects on charge transport (variable range hopping mechanisms) due to the dielectric properties (specifically that of the polaron dielectric contribution) and electronic properties (optical bandgap and Urbach energy) will be discussed.

Page 62

Calculation of Charge Distribution on Doxorubicin in Water

Lokendra Poudel and W.Y. Ching Department of Physics and Astronomy, University of Missouri-Kansas City, Missouri

64111, USA (lpwc2@mail.umkc.edu)

Doxorubicin (C27H29NO11) is a well-known anti-cancer drug used in treating a variety of cancers [1]. Biochemical evidence suggests that this drug primarily makes complexes with DNA by blocking the process of replication and transcription. The charge distribution plays important role in a biological activity of an antibiotic in our body. In our study, we have calculated the charge distribution of doxorubicin in a water environment because water molecules play an important role in governing the structure, stability, dynamic, and function of a biomolecules. Furthermore, we have calculated partial charge of each atom on protonated doxorubicin in water environment since many studies shows that doxorubicin uptake is highly sensitive to pH value.

The deviation of charge from that of neutral atom in unit of electron is called partial charge on an atom. It is denoted by ∆Q (i.e. -∆Q implies gain of electron or electronegative and +∆Q implies loss of electron or electropositive). In this research, the partial charge of Doxorubicin in different environment is calculated using the density functional theory (DFT)-based on orthogonalized linear combination of atomic orbitals (OLCAO) method [2] . Our result shows that, Doxorubicin becomes electropositive from neutral when it is put into the water and electronegative when is protonated in the water.

References [1] Doxorubicin. (2013, July 27). In Wikipedia, The Free Encyclopedia. Retrieved 19:14, August

28, 2013, from http://en.wikipedia.org/w/index.php?title=Doxorubicin&oldid=565988361 [2] Ching, W.Y and Rulis, P. (2012) Electronic Structure Methods for Complex

Materials.Croydon:Oxford.

Page 63

Implementation of Accurate Relativistic Theory in the ab initio Orthogonalized Linear Combination of Atomic

Orbitals Method Patrick R. Thomas, Jr.1, Kazuyoshi Ogasawara2, and Paul Rulis1

1Department of Physics and Astronomy, University of Missouri – Kansas City (prtnpb@mail.umkc.edu)

2Department of Chemistry, Kwansei Gakuin University With increased demand for new technologies, the need for advanced materials with highly tunable electronic and optical properties has risen [1–6]. Laser host crystals are members of an important advanced material family that can be challenging to study computationally because they often have many atoms per unit cell and contain dopant elements with many protons (high Z). Because some electrons in high Z elements move at speeds approaching that of light it becomes necessary to incorporate relativistic effects [7]. The present project implements two key components that are necessary for the eventual development of a fully relativistic version of the Orthogonalized Linear Combination of Atomic Orbitals (OLCAO) [8] computational method. (1) The atomic orbital based wave function has been redesigned using Grasp2K [9] computational method to include most relativistic effects in a simplified way that is immediately implementable in the existing OLCAO code. (2) A new and accurate algorithm for computing the important relativistic kinetic energy term has been adapted from the relativistic Discrete Variational Xα (DV-Xα) [10] method and will be implemented to avoid using a direct but error prone approach involving fourth derivatives of the atomic orbitals.

References [1] A. Zunger, S. Wagner, and P. M. Petroff, J. Electron. Mater. 22, 3 (1993). [2] L. J. Atherton, S. A. Payne, and C. D. Brandle, Annu. Rev. Mater. Sci. 23, 453

(1993). [3] R. Antoni, Infrared Phys. Technol. 41, 213 (2000). [4] T. Jüstel, H. Nikol, and C. Ronda, Angew. Chem. Int. Ed. 37, 3084 (1998). [5] P. Schlotter, R. Schmidt, and J. Schneider, Appl. Phys. Mater. Sci. Process. 64, 417

(1997). [6] C. C. Lin and R.-S. Liu, J Phys Chem Lett 2, 1268 (2011). [7] I. P. Grant, Relativistic Quantum Theory of Atoms and Molecules (Springer, New

York, 2007). [8] Wai-Yim Ching and Paul Rulis, Electronic Structure Methods for Complex

Materials: The Orthogonalized Linear Combination of Atomic Orbitals (Oxford University Press, Oxford, UK, 2012).

[9] P. Jönsson, G. Gaigalas, J. Bieroń, C. F. Fischer, and I. P. Grant, Comput. Phys. Commun. 184, 2197 (2013).

[10] H. Adachi, M. Tsukada, and C. Satoko, J. Phys. Soc. Jpn. 45, 875 (1978).

Page 64

Density Functional Development and Selection in the ab initio Density Functional Theory Based Orthogonalized Linear

Combination of Atomic Orbitals Method

John Thomsen and Paul Rulis

Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA, (jrtktb@mail.umkc.edu)

The orthogonalized linear combination of atomic orbitals (OLCAO) method is a density-functional-theory-based local orbital method [1]. It currently employs the local density approximation (LDA) and local spin density approximation (LSDA) functionals for calculating the exchange and correlation energies and potential. However, these functionals have systematic deficiencies that limit their utility for precision calculations. In order to improve the accounting of electronic exchange and correlation effects there is great interest in advancing the use of numerous other density functionals [2,3]. The OLCAO method has certain inherent advantages for computing large and complex systems such as models of grain boundaries, intergranular glassy film, and biomolecules with a well weighted combination of accuracy and efficiency. These traits arise from the method’s efficient choice of basis function set and through the use of related Gaussian based auxiliary functions for representing the charge density and potential function. However, it is unclear how the choice of density functional will affect the quality of the results within the OLCAO method as applied to different classes of materials. Specifically, the generalized gradient approximation [4] (GGA) to the exchange-correlation contribution is expected to have a significant impact on the accuracy of calculations when working with biomolecules because LDA typically overestimates hydrogen bonding energies, whereas GGA has been shown to yield reasonable results [5,6]. This presentation will explore the application and optimization of a GGA exchange-correlation functional within the OLCAO method with a focused study on biomolecular systems. References [1] Wai-Yim Ching and Paul Rulis, Electronic Structure Methods for Complex Materials: The Orthogonalized

Linear Combination of Atomic Orbitals (Oxford University Press, Oxford, UK, 2012). [2] K. Burke, J. Chem. Phys. 136, 150901 (2012). [3] J. P. Perdew, A. Ruzsinszky, J. Tao, V. N. Staroverov, G. E. Scuseria, and G. I. Csonka, J. Chem. Phys.

123, 062201 (2005). [4] J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996). [5] R. Kaschner and D. Hohl, J. Phys. Chem. A 102, 5111 (1998). [6] P. Deak, T. Frauenheim, and M. Pederson, editors, Computer Simulation of Materials at Atomic Level

(Wiley-VCH, Berlin, 2000).

Page 65

Implementation of a 3-Center Mulliken Overlap Population Analysis Method

Ben Walker and Paul Rulis

Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri, 64110, (baw5ea@mail.umkc.edu)

The electron population analysis formalism developed by R.S. Mulliken in the mid-1950s describes a simple and effective method for computing the strength of a bond between pairs of atoms in a molecule or a solid [1–4]. Because the approach relies on molecular orbital wave functions in the form of a linear combination of atomic orbitals there is an inherent basis dependence to the results. However, substantial physical and chemical insight can still be gained and so it has remained a popular tool for the past half century. An interesting case arises with consideration of elemental boron and boron-rich solids. Because of their molecular icosahedral cage structures they tend to exhibit somewhat uncommon 3-center bonds that are not directly amenable to the 2-center bond order approach. In the study of materials such as amorphous hydrogenated boron carbide (a-BxC:Hy) a deeper understanding of the material properties may be gained via a direct study of the 3-center bonds. In pursuit of this goal, a multi-center bond order scheme has been developed that is compatible with the orthogonalized linear combination of atomic orbitals (OLCAO) method [5], so as to study the alpha rhombohedral structure of elemental boron as an initial test case.

References [1] R. S. Mulliken, J Chem Phys 23, 1833 (1955). [2] R. S. Mulliken, J. Chem. Phys. 23, 1841 (1955). [3] R. S. Mulliken, J. Chem. Phys. 23, 2338 (1955). [4] R. S. Mulliken, J. Chem. Phys. 23, 2343 (1955). [5] W.-Y. Ching and P. Rulis, Electronic Structure Methods for Complex Materials: The

Orthogonalized Linear Combination of Atomic Orbitals (Oxford University Press, USA, 2012).

Page 66

X-Ray Absorption Near Edge Structure of Crystalline Elemental Boron

Liaoyuan Wang, Paul Rulis and Wai-Yim Ching Department of Physics and Astronomy

University of Missouri-Kansas City, Kansas City, MO 64110

(lwang@mail.umkc.edu)

Elemental boron is a complicated material which involves at least six crystalline phases (α-rhombohedral, β-rhombohedral, α-tetragonal, β-tetragonal, γ-orthorhombic, and α-Ga type), amorphous phases, and nano scale structures. The structures of crystalline phases are still controversial due to the extreme synthesizing conditions (high temperature and pressure) and the limitation of measurements. Under such extreme conditions, the structure defects (interstitial site, partial occupations, vacancies, etc.) and foreign non-boron atoms cannot be avoided based on the current experimental techniques. Theoretical simulation on the structures of elemental boron crystals is a subject of considerable importance.

To investigate the local geometrical environment, x-ray absorption near edge structure (XANES) of the six crystalline phases were studied via the ab initio orthogonalized linear combination of atomic orbitals (OLCAO) method. The calculated B-K edge of the α- and β-rhombohedral phases agree well with experiment. Based on this agreement, we predict the XANES spectra [1-3] for the other four crystalline phases. Furthermore, each of the calculated XANES spectra of the five phases that have icosahedral units or clusters of icosahedra show a characteristic set of 3-peak features in the energy range from 190 to 215 eV. These characteristic features were also observed in the XANES spectra of the icosahedron-containing B11C-CBC, a typical boron-rich compound.

References

[1] Paul Rulis, Liaoyuan Wang, Ben Walker and Wai-Yim Ching “Spectral analysis of the electronic structure of γ-B28” Journal of Superhard Materials, 33(6): 394-400 (2011)

[2] Paul Rulis, Liaoyuan Wang, and Wai-Yim Ching “Prediction of γ-B28 ELNES with comparison to α-B12” Phys. Status Solidi RRL 3(5):133-135 (2009)

[3] Liaoyuan Wang et al., unpublished.

Page 67

Electronic structure, Mechanical and Optical properties of CaO·Al2O3 system: A First Principles Study

Altaf Hussain1,2,*, Sitaram Aryal1, Paul Rulis1, and Wai-Yim Ching1 1Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110, USA

2Department of Physics, The Islamia University of Bahawalpur, Bahawalpur, Punjab 63100, Pakistan (*altafiub@yahoo.com)

A comprehensive study of the electronic structure, mechanical and optical properties of calcium aluminates has been performed using density functional theory based OLCAO method. We have calculated five stable phases, (C3A, C12A7-crystal, CA, CA2, and CA6) and one oxygen deficient C12A7-electride phase of the calcium aluminate system. All the five stable phases have wide band gap insulators [1] with the band gap values lying in the range of 3.85 to 4.62 eV. C12A7-electride phase bears a region of metallic bands in the energy range of -1.14 to 0.81 eV. The DOS spectra reveal that all the six calcium aluminate phases are rich in structures. Effective charge and bond order calculations show that Al-O bonds dominate over the Ca-O bonds in all the phases. CA6 has highest bond order density value, while C12A7 has the lowest value. The calculated mechanical properties results on elastic constants, bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio show reasonable agreement with the data (calculated/measured) existing in literature [2]. Optical properties studies show that C3A has the highest value of refractive index and C12A7 the least. Variation of refractive indices with Al2O3 content (x) juggles with x in good agreement with experimental observation.

References [1] J.E. Medvedeva, E.N. Teasley, and M.D. Hoffman, "Electronic band structure and carrier effective mass in calcium aluminates", Phys. Rev. B 76 (2007) 155107 1-6. [2] J. Moon, S. Yoon, R.M. Wentzcovitch, S.M. Clark, and P.J.M. Monteiro, "Elastic properties of tricalcium aluminate from high-pressure experiments and first-principles calculations", J. Am. Ceram. Soc. 95[9] (2012) 2972-2978.

Page 68

Self-assembled Structurally Complex Double-layers of 3-HPLN on Cu(111)

Sumit Beniwal1, Donna A. Kunkel1, James Hooper2, Scott Simpson2, Eva Zurek2, and Axel Enders1,3

1 Department of Physics and Astronomy, University of Nebraska - Lincoln, Lincoln, NE 68588

beniwals99@gmail.com

2 Department of Chemistry, State University of New York at Buffalo, 331 Natural Sciences Complex, Buffalo, NY 14360

3 Nebraska Center for Materials and Nanoscience

The self-assembly of 3-Hydroxyphenalenone (3-HPLN) on various metal surfaces has been studied with scanning tunneling microscopy. 3-HPLN belongs to a group of topological organic ferroelectrics, in which the electric polarization is related to the hydrogen bonds between the molecules. What is fascinating about these ferroelectrics as compared to dipolar rotor ferroelectrics and charge transfer ferroelectrics, is that only a 2D structure is enough to exhibit ferroelectric behavior, and that the coercive fields are typically low. The 2D self-assembled networks on Ag(111) and Au(111) show bonding pattern that are 2D equivalents of bulk crystals. An unexpected new 3D structure is formed on Cu(111), which can be described as chiral Kagome lattice of 3-HPLN. The comparison of the structures formed on surfaces of 3 metals Au, Ag, Cu, and bulk crystal structure has helped establish the structural details of this network, which involves ᴨ-ᴨ stacking and CH-ᴨ bonds, resulting in perpendicular alignment of the molecules in adjacent monolayers.

References Horiuchi, et al, “Hydrogen-bonding molecular chains for high-temperature ferroelectricity” Adv.

Mater. 23, 2098-2103, (2011)

Page 69

Microresonator Magnetic Sensor Xiaolu Yin1, Qianqian Jiao1, Lu Yuan2, and Sy-Hwang Liou1

1Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln

NE 68588-0111 USA yinxiaolu@huskers.unl.edu, jiao-qianqian12@huskers.unl.edu, sliou@unl.edu

2Western Digital Corporation, Fremont, CA USA Lu.Yuan@wdc.com

Magnetic field sensors have many potential applications in technological areas, such as consumer electronics, medical, automotive and telecommunications industries. With the advantage of microelectromechanical systems (MEMS) technology, different types of sensors (including pressure, temperature, and magnetic field sensors) and electronic components can be integrated on a single chip. The microcantilever torque magnetometer (MTM) system is an experimental technique for studying magnetic nano-structures with a magnetic moment resolution in the range of 10-14 Am2 to 10-19 Am2 [1]. Based on the principle of microcantilever torque magnetometer, we developed a new high-sensitive magnetic field sensor. This sensor consists of a soft magnetic Fe77.5Si7.5B15 wire and a torsion oscillator, which is fabricated with MEMS technology. Our sensor has the detectable magnetic field sensitivity within 5 nT under ambient conditions [2]. We estimate that the sensitivity of microresonator magnetic sensors could be further improved to a few pico-Tesla by modifying the spring constant of the cantilever and incorporating phase-locked cantilever magnetometry.

References [1] M. D. Chabot, J. M. Moreland, L. Gao, S. H. Liou, and C. W. Miller, “Novel fabrication of

micromechanical oscillators with nanoscale sensitivity at room temperature,” J. Microelectromech. Syst., vol. 14, p. 1118, 2005.

[2] Xiaolu Yin, Qianqian Jiao, Lu Yuan, and Sy-Hwang Liou, “MEMS Torsion Oscillator Magnetic Field Sensor”, IEEE Trans. Magn., vol. 49, p. 3890, 2013.

Page 70

Graphene Field effect Sensors for the Study of Ferroelectric Thin Films

A. Rajapitamahuni1, J. Hoffman2, C.H. Ahn2 and X. Hong1 1Department of Physics and Astronomy, University of Nebraska-Lincoln

(anil21@huskers.unl.edu) 2Department of Applied Physics, Yale University

We have demostrated the working principle of graphene field effect sensors for the study of the pyroelectric, dielectric and ferroelectric properties of ferroelectric thin films [1]. Using off-axis radio frequency magnetron sputtering, we have grown epitaxial single crystalline Pb(Zr,Ti)O3 (PZT) and (Ba,Sr)TiO3 (BSTO) thin films of 100-300 nm thick on (001) Nb doped SrTiO3 substrates. X-Ray and AFM characterizations show the films have high crystallinity and smooth surfaces. Graphene flakes are mechanically exfoliated on the ferroelectric thin films, and single to few layer graphene are indentified by Raman spectroscopy and fabricated into field effect devices. We extract the carrier density in graphene from Hall effect measurements and use it to probe the polarization (P) change of the ferroelectric gate. At zero gate bias, we measure the temperature dependence of carrier density, which is induced by the pyroelectric effect of the gate. At 300 K, dP/dT yields pyroelectric coefficients of ~-15 nC/cm2K for PZT and ~-20 nC/cm2K for BSTO. Below the coercive voltage, we measure the gating efficiencies of the ferroelectric thin films, which correpsond to a dielectric constant of ~50 for PZT and ~100 for BSTO at 5 K. These measured values are comparable to the previously reported values on PZT and BSTO thin films. As the gate bias exceeds the coercive voltage, ferroelectric switching induced hysteresis starts to develop in both resistance and carrier density. From the carrier density hysteresis, we find the remnant polarization of BSTO thin films at 10 K is ~5 μC/cm2 , which saturates to ~10 μC/cm2 at high gate voltage. Above 100 K, an anti-hysteresis behavior gradually dominates the switching behavior, which is activated by the combined effects of electric field and temperature. We attribute this anti-hysteresis to the dyanmic screening of the polarization due to the presence of interfacial charges. In conclusion, the low density of states of graphene makes it a sensitive tool to study ferroelectric thin films, and the interface chemistry plays an important role in the performance of graphene-ferroelectric oxide hybrid devices.

References [1] A. Rajapitamahuni et al, “Examining Graphene Field Effect sensors for Ferroelectric thin

film studies”, Nano Lett. (in press) (2013).

Page 71

Domain wall roughness and creep in nanoscale crystalline ferroelectric polymers

Z. Xiao1*, Shashi Poddar1, Stephen Ducharme1,2, and X. Hong2 1Department of Physics and Astronomy, University of Nebraska-Lincoln, NE 68588

(*zhiyong@huskers.unl.edu) 2Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, NE

68588

Ferroelectric polymers such as ploy(vinylidene-fluoridethylene) (PVDF-TrFE) can preserve the ferroelectric ground state as the system dimensionality D is reduced from the bulk (D = 3) to the two dimensionality limit (D = 2) [1]. Critical information on how ferroelectricity evolves with the system dimension can be gained by studying the static configuration and dynamic response of ferroelectric domain walls (DWs). These properties of DWs also determine the fundamental density limit and ultimate operation speed of 2D ferroelectric devices.

In a d-dimensional system, it has been shown that DW can be treated as a (d-1) dimensional elastic manifold with presence of random disorder potential. The static roughness of DW can be described by scaling behavior with a roughness exponent ζ. When subject to a small electric field, the propagation of the DWs follows a nonlinear creep mode with creep exponent µ. The roughness and the creep exponents carry the critical information of the dimensionality and the dominating disorder of the system.

In this work, we report the scanning probe study of DW roughness and creep behavior in 6-20 monolayer crystalline PVDF-TrFE films (11-36 nm thick) prepared by Langmuir Blodgett technique. The piezo-response force microscopy studies of the DWs in PVDF-TrFE films reveal the roughness exponent ζ to be 0.40 to 0.48 and the creep exponent to be 0.20 to 0.29, which yield an unexpected dimensionality of ~1.5 that is independent of film thickness, in sharp contrast to DWs observed in ferroelectric oxide Pb(Zr,Ti)O3 films of similar thickness [2]. The fractal dimensionality and weak thickness dependence suggest that the interlayer interaction plays a minor role in ferroelectric domain nucleation and propagation, and we propose that the DW can be deroughened by the disordered in-plane component of the polarization. This type of correlated disorder is introduced by the intrinsic orientation of polarization, which can be easily implemented into crystalline ferroelectrics. Our results thus suggest an effective and relatively low cost route to achieve higher lateral density in nanoscale ferroelectric-based data storage and sensing devices.

References [1] A. V. Bune et al, “Two-dimensional ferroelectric films”, Nature 391, 874 (1998). [2] Z. Xiao et al, “Domain wall roughness and creep in nanoscale crystalline ferroelectric

polymer”, Appl. Phys. Lett. accepted (2013).

Page 72

Novel Magnetic Nanostructured Multilayer for High Sensitive Magnetoresistive Sensors

Xiaolu Yin, Sy-Hwang Liou

University of Nebraska- Lincoln The critical parameters for a high sensitive magnetoresistive sensor include high permeability, good linearity and low noise. All these parameters are related to better control of the magnetic nanostructured of multilayers in magnetic tunnel junctions (MTJ). The sensitivity of the sensor is related to large tunnel magnetoresistance ratio (TMR) and low saturation magnetic field (Hs) in free layer of MTJ junctions, which means high susceptibility. The linear nonhysteretic response of the sensor is related to both low coercivity field (Hc) in free layer, and also good orthogonal magnetization configuration between free layer and pinned layer. The noise of the sensor is related to the interface between the layers and their nanostructures. In this poster, we presented a few projects that improve the sensitive magnetoresistive sensor through the variation of magnetic nanostructures in the magnetic tunnel junctions. These magnetic nanostructures are varied by annealing temperatures, different annealing environments, the thickness of the free layer in MTJ, as well as through the exchange interaction using ferromagnetic- ferromagnetic coupling within the free layer of MTJ. We show a magnetoresistive sensor with a sensitivity as high as 1916 %/mT. This magnetic sensor only dissipates 20 μW of power while operating under an applied voltage of 1 V. 1. S. H. Liou, Xiaolu Yin, Stephen E. Russek, Ranko Heindl, F. C. S. Da Silva, John

Moreland, David P. Pappas, L Yuan and J. Shen, “Picotesla Magnetic Sensors for Low Frequency Applications”, IEEE Trans. on Magnetics, 47, 3740(2011).

2. Xiaolu Yin, S. H. Liou, “Novel Magnetic Nanostructured Multilayer for High Sensitive Magnetoresistive Sensor”,(invited only) IEEE Sensors 2012 Conference, 2090 (2012)

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