Computational Materials at Texas · Genius is one percent inspiration and ninety-nine percent...
Transcript of Computational Materials at Texas · Genius is one percent inspiration and ninety-nine percent...
Computational Materials at Texas
Professor Jim ChelikowskyRoom 4.324 ACE
Email: [email protected]: 2-9083
Web site: http://www.ices.utexas.edu
Personal website: http://tesla.ices.utexas.edu
Background• PhD in Physics from University of California, Berkeley
• Postdoc at Bell Labs
• Exxon Research and Engineering
• University of Minnesota
• University of Texas, arrived January 2005. Positions in Chem E, Physics and Chemistry/Biochemistry
• Research interests: materials science and computational physics
Current Group Members
Postdocs: Tzu-Liang Chan, Amy Khoo, Jaehyeon Eom, and Na Sai (not pictured is Jonathan Moussa.)
Students: Hyunwook Kwak (ChemE), Grady Schofield (CAM), and Jason Han (Physics).
Funding Sources
• National Science Foundation: New Institute for Advanced Electronic Materials
• Department of Energy: Nanoscience
Institute for the Theory of Advanced Materials in Information
Technology
http://www.ices.utexas.edu
Genius is one percent inspiration and ninety-nine percent perspiration!- Thomas Edison
Why do simulation and modeling?
If Mr. Edison didnʼt perspire so much he would get more accomplished! - Nikola Tesla
If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search. [...] I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor. — Nikola Tesla
Mythbusters:Burn the stack, pickup the needle.
Role of Electronic Materials
Semiconductors have been widely recognized as a key enabler for the new economy described earlier. In a recent study on the economic impact of America's manufacturing industries, entitled "Turbocharging the U.S. Economy," the semiconductor industry was identified as the largest, contributing over 20 percent more to the U.S. GDP than the next largest sector (automobiles).
Circa 1960: Early transistors
Circa 2000: 40 million transistors
SILICON!
DALLAS (May 10, 1954) - A revolutionary new
electronic product--long predicted and awaited--
became a reality today with the announcement by
Texas Instruments Incorporated of the start of
commercial production on silicon transistors. By
using silicon instead of germanium, the initial
commercial silicon transistor immediately raises
power outputs and doubles operating
temperatures! The potential application of this
entirely new transistor is so great that major
electronics firms have been conducting silicon
experiments for some time. -- Press Release
Texas Instruments.
Silicon: 1954
From the Transistor Museum.
• “Gordon Moore made his famous observation in 1965, just four years after the first planar integrated circuit was discovered. The press called it "Moore's Law" and the name has stuck. In his original paper, Moore predicted that the number of transistors per integrated circuit would double every 18 months.” --Intel website
Moore’s Law
Intel is now a “nanotechnology company.”
Examples of Materials of Interest to Intel....
Research Goals:
• Understand properties of electronic materials
• Examine hypothetical or experimentally inaccessible regimes
• Predict properties and new materials
Semiconductor nanostructures
• Reduced size and dimensionality: quantum dots, nanowires (quantum wires), quantum wells.• Quantum confinement: electron (hole) exitations are strongly quantized – Quantum dot: 3D confinement– Nanowire: 2D confinement• Industrial applications: – Unique building blocks in nanoelectronics and photonics.– Device applications: optoelectronics, photovoltaics, thermoelectrics and sensors.
The optical properties of
semiconductors like CdSe
can be tuned to span the
optical region of the
spectrum by varying the
size of the dot. At left, the
dot size ranges from roughly
4 to 7 nm in diameter.
Optical Excitations in Semiconductor Quantum Dots
Colloidal solutions of CdSe quantun dots of different sizes
At small dimensions, electrons experience quantum confinement. This is direct consequence of the uncertainty principle. As electrons become localized their energy increases approximately as the inverse square of the dot radius.
R
Quatum dot of radius R
Quantum calculations can be used to predict electronic and optical properties at the nano-scale as well as other properties. Predictions of these calculations confirm the role of quantum confinement.
Silicon Dot
Nanowires of Semiconductors
Brian Korgel’s group
1 µm1 µm
3 µm3 µm
Ge Si
GaAs GaP
InP nanowire
d
Three layers along [111] direction is enough to converge the optical gap to 0.01 eV for pure dot.
Energy gaps of quantum dots and nanowires: 3D versus 2D confinement
Quantum confinement in the InP quantum dots is stronger than than
in the nanowires.
Active Projects• Electrical transport in nanoscale devices• New materials for spintronic applications
• Evolution of doping properties in nanocrystals and nanowires
• Magnetic materials
• Developing new algorithms for predicting the electronic and magentic properties of materials