Bandgap engineering of Janus MoSSe monolayer implemented by Se vacancy

Vacancy defects in 2D materials provide opportunities to tailor local physical, structural and electronic properties of point and linear vacancies in Janus MoSSe monolayers. In this paper, we studied vacancy formation in Janus MoSSe monolayers using ab initio density functional theory and observed that all vacancies are preferentially formed in the Se layer. In the case of point defects with more than two vacancies, a zigzag line feature is obtained for the lowest formation energy. In the case of infinite linear defects, the zigzag vacancy lines preferred to be distant from each other. The bandgap of a Janus MoSSe monolayer can be modulated by the concentration of vacancies. The bandgap energy decreased from 1.080 eV to 0.675 eV with the increase in the number of point vacancies. However, it is observed to oscillate around 0.530 eV with the increase of distance between the vacancy lines in the case of linear vacancies. This work is very useful in bandgap engineering of optical and electronic devices based on MoS₂.