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.