first principles simulations of nanoelectronic devices
DESCRIPTION
First principles simulations of nanoelectronic devices. Jesse Maassen (Supervisor : Prof. Hong Guo) Department of Physics, McGill University, Montreal, QC Canada. Year. Channel length. 2012. 22 nm. 2015. 16 nm. 2018. 11 nm ?. (Source: ITRS 2010). Line of ~ 50 atoms. - PowerPoint PPT PresentationTRANSCRIPT
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
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)
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
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)
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)
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
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)
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)
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.
December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Transport properties :
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)
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.
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)
December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Maassen et al., Nano. Lett. 11, 151 (2011)
December 2, 2011 Ph.D. Thesis Presentation
Application : Graphene-metal interface
Ni(111) contact :
Maassen et al., Nano. Lett. 11, 151 (2011)
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 ?
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.
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
December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
Maassen and Guo, preprint to be submitted
December 2, 2011 Ph.D. Thesis Presentation
Application : Localized doping in Si nano-transistors
Maassen and Guo, preprint to be submitted
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
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
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.
December 2, 2011 Ph.D. Thesis Presentation
Thank you!
Questions ?