Date of Award

7-1-2013

Degree Type

Thesis

University or Center

Clark Atlanta University(CAU)

School

School of Arts and Sciences

Degree Name

M.S.

Department

Physics

First Advisor

Dr.Xiao-OianWang

Second Advisor

Dr. Michael D. Williams

Third Advisor

Dr. Zhifan Chen

Abstract

Recent experimental work has demonstrated production of quasi free-standing graphene by methane intercalation. The intercalation weakens the coupling of adjacent graphene layers and yields Dirac fermion behaviour of monolayer graphene. We have investigated the electronic characteristics of methane intercepted graphene bilayer under a perpendicularly applied electric field. Evolution of the band structure of intercalated graphene as a function of the bias is studied by means of density-functional theory including interlayer van der Waals interactions. The implications of controllable band gap opening in methane-intercalated graphene for future device applications are discussed.

Noncovalent functionalization provides an effective way to modulate the electronic properties of graphene. Recent experimental work has demonstrated that hybrids of dipolar phototransductive molecules tethered to graphene are reversibly tunable in doping. We have studied the electronic structure characteristics of chromophore/graphene hybrids using dispersion-corrected density functional theory. The Dirac point of noncovalently functionalized graphene shifts upward via cis-trans isomerism, which is attributed to a change in the chromophore's dipole moment. Our calculation results reveal that the experimentally observed reversible doping of graphene is attributed to the change in charge transfer between the light-switchable chromophore and graphene via isomerization. Furthermore, we show that by varying the electric field perpendicular to the supramolecular functionalized graphene, additional tailoring of graphene doping can be accomplished.

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