Electronic Properties of Defective Janus MoSSe Monolayer.

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) hold great promise in electronics and optoelectronics due to their novel electronic and optical properties. In TMDCs, structural defects are inevitable and might play a decisive role in device performance. In this work, point defects, line vacancies, and 60° grain boundaries (GBs) are explored in 2D Janus MoSSe, a new member to the family of TMDCs, by means of the first-principles calculations. S and Se vacancies are found to be the most favorable point defects, and they tend to aggregate along the zigzag direction to form line vacancies. Comparing with isolated point defects, line vacancies induced in-gap states are more dispersive. In particular, 60° GBs behave as one-dimensional metallic quantum wires, as a consequence of the polar discontinuity. Thus, effectively controlling the formation of defects at nanoscale brings new electronic characteristics, providing new opportunities to broaden the applications of 2D TMDCs.