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First principles simulations of nanoelectronic devices

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First principles simulations of nanoelectronic devices Jesse Maassen (Supervisor : Prof. Hong Guo) Department of Physics, McGill University, Montreal, QC Canada – PowerPoint PPT presentation

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Title: First principles simulations of nanoelectronic devices


1
First principles simulations of nanoelectronic
devices
Jesse Maassen (Supervisor Prof. Hong
Guo) Department of Physics, McGill University,
Montreal, QC Canada
2
Why first principles theory?
3
Why first principles theory?
4
How to calculate transport properties?
Taylor et al., PRB 63, 245407 (2001) Waldron et
al., PRL 97, 226802 (2006) Maassen et al., IEEE
(submitted)
5
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)
6
Applications.
  • Graphene-metal interface
  • Localized doping in Si nano-transistors
  • Dephasing in nano-scale systems

Maassen and Guo, preprint to be submitted
7
Applications.
  • Graphene-metal interface
  • Localized doping in Si nano-transistors
  • Dephasing in nano-scale systems

Maassen et al., PRB 80, 125423 (2009)
8
Applications.
  • Graphene-metal interface
  • Localized doping in Si nano-transistors
  • Dephasing in nano-scale systems

Maassen et al., PRB 80, 125423 (2009)
9
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).
  • Theoretical studies exclude accurate treatment of
    electrodes.
  • How does the graphene/metal interface affect the
    response of a device?

10
Application Graphene-metal interface
  • Transport properties

11
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.

Maassen et al., Appl. Phys. Lett. 97, 142105
(2010) Maassen et al., Nano. Lett. 11,151 (2011)
12
Application Graphene-metal interface
  • Ni(111) contact
  • Linear dispersion bands near Fermi level.
  • Zero band gap.
  • States only in the vicinity of K.

13
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)
14
Application Graphene-metal interface
  • Ni(111) contact

15
Application Graphene-metal interface
  • Ni(111) contact

16
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 ?

17
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.
18
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
19
Application Localized doping in Si
nano-transistors
Maassen and Guo, preprint to be submitted
20
Application Localized doping in Si
nano-transistors
Maassen and Guo, preprint to be submitted
21
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
22
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
23
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.

24
Thank you!
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