Title: First principles simulations of nanoelectronic devices
1First principles simulations of nanoelectronic
devices
Jesse Maassen (Supervisor Prof. Hong
Guo) Department of Physics, McGill University,
Montreal, QC Canada
2Why first principles theory?
3Why first principles theory?
4How to calculate transport properties?
Taylor et al., PRB 63, 245407 (2001) Waldron et
al., PRL 97, 226802 (2006) Maassen et al., IEEE
(submitted)
5Applications.
- 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)
6Applications.
- Graphene-metal interface
- Localized doping in Si nano-transistors
- Dephasing in nano-scale systems
Maassen and Guo, preprint to be submitted
7Applications.
- Graphene-metal interface
- Localized doping in Si nano-transistors
- Dephasing in nano-scale systems
Maassen et al., PRB 80, 125423 (2009)
8Applications.
- Graphene-metal interface
- Localized doping in Si nano-transistors
- Dephasing in nano-scale systems
Maassen et al., PRB 80, 125423 (2009)
9Application Graphene-metal interface
- 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).
- Theoretical studies exclude accurate treatment of
electrodes.
- How does the graphene/metal interface affect the
response of a device?
10Application Graphene-metal interface
11Application Graphene-metal interface
- Cu, Ni and Co (111) have in-place lattice
constants that almost match that of graphene.
- Equilibrium interface structure determined from
atomic relaxations.
Maassen et al., Appl. Phys. Lett. 97, 142105
(2010) Maassen et al., Nano. Lett. 11,151 (2011)
12Application Graphene-metal interface
- Linear dispersion bands near Fermi level.
- Zero band gap.
- States only in the vicinity of K.
13Application Graphene-metal interface
- Strong hybridization with metal
- Band gap opening
- Graphene is spin-polarized
Maassen et al., Nano. Lett. 11, 151 (2011)
14Application Graphene-metal interface
15Application Graphene-metal interface
16Application Localized doping in Si
nano-transistors
- 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 ?
17Application 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.
18Application Localized doping in Si
nano-transistors
- Lowest G with doping in the middle of the channel.
Maassen and Guo, preprint to be submitted
19Application Localized doping in Si
nano-transistors
Maassen and Guo, preprint to be submitted
20Application Localized doping in Si
nano-transistors
Maassen and Guo, preprint to be submitted
21Application Localized doping in Si
nano-transistors
- Variations in G increase dramatically with L.
Maassen and Guo, preprint to be submitted
22Application Localized doping in Si
nano-transistors
- Variations in G increase dramatically with L.
Maassen and Guo, preprint to be submitted
23Summary
- 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.
24Thank you!
Questions ?