Effect of Al$_2$O$_3$ deposition on electronic Transport in Graphene: DFT-NEGF study

In order to screen the charged impurities and to prevent the adsorption of contaminant on graphene, the deposition of high-k materials such as Al$_2$O$_3$ on graphene surface is important issue for graphene device application. Since the interfacial structure of graphene and high-k materials are not identified, theoretical study on the interfacial structure dependence on electronic transport is highly demanded. In this paper, we performed the electronic transport simulation in graphene under Al$_2$O$_3$ based on the density functional theories (DFT) and nonequilibrium Green's function method (NEGF). We investigated the effect of Al$_2$O$_3$ surface termination on the electronic transport properties. According to the calculation of stability of interfaces and electronic structures, the graphene's linear band structure is preserved in O$_2$ deficient condition. In O$_2$ rich condition, on the other hand, the graphene's unique electronic structure is disturbed. These properties are important for the electronic transport in graphene under Al$_2$O$_3$. Graphene shows relatively good transport properties in O$_2$ deficient condition, but transport is considerably suppressed in O$_2$ rich condition. Our results suggest O$_2$ deficient condition is desirable for the device application.