First-principles study of vacancy defects at interfaces between monolayer MoS and Au.

The performance of MoS based devices is closely related to the quality and defect morphology of the monolayer MoS deposited on metal. First-principles calculations were performed to investigate the vacancy effects of Au-mMoS contact. Four possible S-vacancy and a Mo-vacancy were considered in our calculations. Energetic studies show that S-vacancies are easier to form than Mo-vacancy in Au-mMoS contact, while S-vacancy (hollow site at interface, V) has the lowest formation energy under Mo-rich environments. Electron and charge redistribution analysis of defective Au-mMoS contact indicate that the lower contact resistance and higher electron injection efficiency of defective Au-MoS contact than perfect ones. Notably, the S-vacancy at top layer showed better electronic performance than that at bottom layer of monolayer MoS in the contact. High quality n-type Au-mMoS contact can therefore be expected through defect engineering.