Noninvasive metal contacts in chemically derived graphene devices

We study the properties of gold contacts on chemically derived graphene devices by scanning photocurrent microscopy and gate-dependent electrical transport measurements. In the as-fabricated devices, negligible potential barriers are found at the gold/graphene interface, reflecting the noninvasive character of the contacts. Device annealing above 300 degrees C leads to the formation of potential barriers at the contacts concomitant with metal-induced p-type doping of the sheet as a consequence of the diffusion of gold from the electrodes. The transfer characteristics of the chemically derived graphene devices point toward the suppression of Klein tunneling in this material.