Engineering sulfur vacancies in WS2/Au interface toward ohmic contact

Achieving ohmic contact at the interface between two-dimensional semiconductors and metallic electrodes is important for developing high-performance optoelectric devices. In this work, the first-principles calculations are engaged to investigate how sulfur vacancies modify the electronic structures of the WS2/Au interface. The Schottky barrier height is found to decrease with increasing density of surface sulfur vacancies. The presence of interfacial sulfur vacancies further reduces the barrier height, due to the enhanced interlayer charge transfer. The interfacial sulfur defects also change the stacking order into a hollow-over-hollow configuration, which features an ohmic contact due to the interfacial bond formation. This work has revealed the dependence of the electronic structure of WS2/Au contact on the sulfur vacancy density, sulfur vacancy position and stacking order. The results gain insight into understanding the electronic structures and transport properties at the WS2/Au interface.