Quantum transport and bulk calculations for graphene-based devices

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Title: Quantum transport and bulk calculations for graphene-based devices
Author: Basu, Dipanjan
Abstract: As devise sizes approach the nanoscale , novel device geometries and materials are considered , and new types of essential physics becomes important and new physical switching mechanism are considered , and as our intuitive understanding of device behavior is stretched accordingly , increasing first -principles simulation is required to understand and predict device behavior . To this end , initially I worked to capture the richness of the confinement and transport physics in quantum -wire devices . I developed an efficient fully three dimensional atomistic quantum transport simulator within a nearest -neighbor atomistic tight -binding framework . However , I soon adapted this work to the study of transport in graphene mono -layer and bilayer nano -ribbons . Motivated by proposals for use of nano -ribbons to create band gaps in otherwise gapless graphene monolayers , I studied the effects of edge disorder in such graphene nano -ribbon FETs . I found that ribbon widths sufficiently narrow to produce useful bandgaps , would also lead to an extreme sensitivity to ribbon -edge roughness and associated performance degradation and device -to -device variability . Going beyond conventional switching but staying with the graphene material system , to model electron -hole condensation in two graphene monolayers separated by a tunnel dielectric potentially beyond room temperature , I developed a self -consistent atomistic tight -binding treatment of the required interlayer exchange interaction within non -local Hartree -Fock mean -field theory . Such condensation , associated many -body enhanced interlayer current flow , and gate -control thereof is the basis for the beyond -CMOS Bilayer -pseudoSpin Field Effect Transistor (BiSFET ) proposed by colleagues . I studied the effect of various system parameters and on interlayer charge imbalance on the strength of the condensate state . I also modeled the critical current , the maximum interlayer current that can be supported by the condensate , its detailed dependence on the nature and strength of the required interlayer bare tunneling and on charge imbalance . The results presented here are expected to be used to refine devices models of the BiSFET , and may serve as guides to experiments to observe such a condensate state .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2081
Date: 2011-02-02


Quantum transport and bulk calculations for graphene-based devices. Doctoral dissertation, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2081 .

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