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Graphene-metal contact resistance is governed by both intrinsic and extrinsic factors. Intrinsically, both the density of states bottleneck near the Dirac point and carrier reflection at the graphene-metal interface lead to a high contact resistance. Moreover, graphene exhibits insulating behavior for out-of-the-plane conduction. Extrinsically, surface contamination introduced by photoresist residue or different adsorbed species during standard lithography processing alters graphenes intrinsic properties by uncontrolled doping and increased scattering which results in high and inconsistent contact resistance. Here we demonstrate a femto-second laser assisted direct patterning of graphene microstructures that enables us to study both intrinsic and extrinsic effects on the graphene-metal interface. We show that a clean graphene-metal interface is not sufficient to obtain contact resistance approaching the intrinsic limit set by the quantum resistance. We also demonstrated that unlike CVD graphene, edge state conduction (or end-contact) is not spontaneously formed by metal deposition in case of graphene grown on SiC(0001). We conclude that for epitaxial graphene, intentional end-contact formation is necessary to obtain contact resistance near the quantum contact resistance limit.
Graphene oxide (GO) flakes have been deposited to bridge the gap between two epitaxial graphene electrodes to produce all-graphene devices. Electrical measurements indicate the presence of Schottky barriers (SB) at the graphene/graphene oxide junctio
Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undope
We present Raman spectroscopy measurements of non-etched graphene nanoribbons, with widths ranging from 15 to 160 nm, where the D-line intensity is strongly dependent on the polarization direction of the incident light. The extracted edge disorder co
We perform density functional theory calculations for the determination of the structural and electronic properties of epitaxial graphene on 4H-SiC(000$bar{1}$). Using commensurate supercells that minimize non-physical stresses we show that, in contr
The broadband and ultrafast photoresponse of graphene has been extensively studied in recent years, although the photoexcited carrier dynamics is still far from being completely understood. Different experimental approaches imply either one of two fu