Charge transfer region at the edge of metal contacts on graphene and its impact on contact resistance measurement

As graphene devices are increasingly developed, the metal-graphene contact has acquired an important role, because recently reported contact resistances are not good enough to maintain the intrinsic advantages of graphene in scaled devices. It is known that a metal on graphene can provide a strong doping effect associated with its work function difference and graphene´s small density of states [1], [2]. When the carrier densities of the graphene channel and the metal-covered graphene are different (fig.1), a charge transfer region (CTR) near the contact edge is formed [2], [3], in which the potential and carrier density gradually change to their equilibrium state. In this study, we investigate various factors which can affect the CTR length, and the impacts of CTR on contact resistance measurement.