Electrical Contact between an Ultrathin Topological Dirac Semimetal and a Two-Dimensional Material
Abstract
Ultrathin films of topological Dirac semimetal, Na3Bi, has recently been revealed as an unusual electronic materials with field-tunable topological phases. Here we investigate the electronic and transport properties of ultrathin Na3Bi as an electrical contact to two-dimensional (2D) metal, i.e. graphene, and 2D semiconductor, i.e. MoS2 and WS2 monolayers. Using combined first-principle density functional theory and nonequilibrium Green's function simulation, we show that the electrical coupling between Na3Bi bilayer thin film and graphene results in a notable interlayer charge transfer, thus inducing sizable n-type doping in the Na3Bi/graphene heterostructures. In the case of MoS2 and WS2 monolayers, the lateral Schottky transport barrier is significantly lower than many commonly studied bulk metals, thus unraveling Na3Bi bilayer as a high-efficiency electrical contact material for 2D semiconductors. These findings opens up an avenue of utilizing topological semimetal thin film as electrical contact to 2D materials, and further expands the family of 2D heterostructure devices into the realm of topological materials.