Three-dimensional macroporous nanoelectronic networks as ...
First principles simulations of nanoelectronic devices
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December 2, 2011 Ph.D. Thesis Presentation
First principles simulations of nanoelectronic devices
Jesse Maassen
(Supervisor : Prof. Hong Guo)
Department of Physics, McGill University,
Montreal, QC Canada
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December 2, 2011 Ph.D. Thesis Presentation
Why first principles theory?
Line of ~ 50 atoms
2012 22 nm
Year Channel length
2015 16 nm
2018 11 nm ?(Source: ITRS 2010)
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December 2, 2011 Ph.D. Thesis Presentation
Why first principles theory?
Science Engineering
Atomic structure :
surfaces, chemical bonding, interfaces, dissimilar materials, charge transfer, roughness, variability, …
tunneling, conductance quantization, spin-transport, …
Quantum effects :First principles
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December 2, 2011 Ph.D. Thesis Presentation
How to calculate transport properties?
Taylor et al., PRB 63, 245407 (2001)Waldron et al., PRL 97, 226802 (2006)Maassen et al., IEEE (submitted)
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December 2, 2011 Ph.D. Thesis Presentation
Applications.
Graphene-metal interface
Localized doping in Si nano-transistors
Dephasing in nano-scale systems
Maassen et al., Appl. Phys. Lett. 97, 142105 (2010); Maassen et al., Nano. Lett. 11,151 (2011)
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December 2, 2011 Ph.D. Thesis Presentation
Applications.
Graphene-metal interface
Localized doping in Si nano-transistors
Dephasing in nano-scale systems
Maassen and Guo, preprint to be submitted
![Page 7: First principles simulations of nanoelectronic devices](https://reader035.fdocuments.net/reader035/viewer/2022062517/568136e3550346895d9e7dff/html5/thumbnails/7.jpg)
December 2, 2011 Ph.D. Thesis Presentation
Applications.
Graphene-metal interface
Localized doping in Si nano-transistors
Dephasing in nano-scale systems
Maassen et al., PRB 80, 125423 (2009)
![Page 8: First principles simulations of nanoelectronic devices](https://reader035.fdocuments.net/reader035/viewer/2022062517/568136e3550346895d9e7dff/html5/thumbnails/8.jpg)
December 2, 2011 Ph.D. Thesis Presentation
Applications.
Graphene-metal interface
Localized doping in Si nano-transistors
Dephasing in nano-scale systems
Maassen et al., PRB 80, 125423 (2009)
![Page 9: First principles simulations of nanoelectronic devices](https://reader035.fdocuments.net/reader035/viewer/2022062517/568136e3550346895d9e7dff/html5/thumbnails/9.jpg)
December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Motivation :
Graphene has interesting properties (i.e., 2D material, zero gap, linear dispersion bands, …).
For electronics, all graphene sheets must be contacted via metal electrodes (source/drain).
How does the graphene/metal interface affect the response of a device?
Theoretical studies exclude accurate treatment of electrodes.
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Transport properties :
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Atomic structure :
Cu, Ni and Co (111) have in-place lattice constants that almost match that of graphene.
Equilibrium interface structure determined from atomic relaxations.
MetalMetal
eq
Maassen et al., Appl. Phys. Lett. 97, 142105 (2010); Maassen et al., Nano. Lett. 11,151 (2011)
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Linear dispersion bands near Fermi level.
Zero band gap.
States only in the vicinity of K.
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Strong hybridization with metal
Band gap opening
Graphene is spin-polarized
Maassen et al., Nano. Lett. 11, 151 (2011)
: Top-site C(pz): Hollow-site C(pz): Ni(dZ
2)
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Maassen et al., Nano. Lett. 11, 151 (2011)
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December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Maassen et al., Nano. Lett. 11, 151 (2011)
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December 2, 2011 Ph.D. Thesis Presentation
CHANNEL
Application : Localized doping in Si nano-transistors
Motivation :
Leakage current accounts for 60% of energy in transistors.
Two sources : (i) gate tunneling and (ii) source/drain tunneling.
How can highly controlled doping profiles affect leakage current ?
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
Structure: n-p-n and p-n-p. Channel doping: B or P. L = 6.5 nm 15.2 nm Si band gap = 1.11 eV
Technical details regarding random doping, large-scale modeling and predicting accurate semiconductor band gaps can be found in the thesis.
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
GMAX / GMIN ~ 50.
Lowest G with doping in the middle of the channel.
Maassen and Guo, preprint to be submitted
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
Maassen and Guo, preprint to be submitted
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
Maassen and Guo, preprint to be submitted
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
G decreases with L.
Variations in G increase dramatically with L.
Maassen and Guo, preprint to be submitted
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December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
G decreases with L.
Variations in G increase dramatically with L.
Maassen and Guo, preprint to be submitted
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December 2, 2011 Ph.D. Thesis Presentation
Summary
First principles transport theory is a valuable tool for quantitative predictions of nanoelectronics, where atomic/quantum effects are important.
I determined that the effect of metallic contacts (Cu, Ni, Co) can significantly influence device characteristics. I found that the atomic structure of the graphene/metal interface is crucial for a accurate treatment.
My simulations on localized doping profiles demonstrated how leakage current can be substantially reduced in addition to alleviating device variations.
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December 2, 2011 Ph.D. Thesis Presentation
Thank you!
Questions ?