First Principles Study of Contact Resistance across Nickel-Treated-Graphene-MoS$_{2}$ Interfaces

Recently, Ni-treated-graphene electrodes were fabricated on MoS$_{2}$ using a dry transfer technique and metal-catalyzed graphene treatment process, yielding contact resistances as low as 200 $\Omega \mu $m and a substantial contact enhancement of $\sim$ 2 orders of magnitude relative to Ni-MoS$_{2}$ interfaces. By performing a Schottky barrier height (SBH) analysis on Ni-MoS$_{2}$ and Ni-graphene-MoS$_{2}$ interfaces using first-principles DFT calculations, we have found that the smaller contact resistance in Ni-treated-graphene-MoS$_{2}$ can be attributed to the smaller SBH of Ni-graphene-MoS$_{2}$ contacts. This reduction in SBH can in turn be related to the lower work function of Ni-graphene electrodes relative to Ni. The effect of Ni treatment further reduces the contact resistance due to stronger coupling between Ni and graphene edges.