The effects of point defect type, location, and density on the Schottky barrier height of Au/MoS(2) heterojunction: a first-principles study

Using DFT calculations, we investigate the effects of the type, location, and density of point defects in monolayer MoS(2) on electronic structures and Schottky barrier heights (SBH) of Au/MoS(2) heterojunction. Three types of point defects in monolayer MoS(2), that is, S monovacancy, S divacancy and Mo(S) (Mo substitution at S site) antisite defects, are considered. The following findings are revealed: (1) The SBH for the monolayer MoS(2) with these defects is universally higher than that for its defect-free counterpart. (2) S divacancy and Mo(S) antisite defects increase the SBH to a larger extent than S monovacancy. (3) A defect located in the inner sublayer of MoS(2), which is adjacent to Au substrate, increases the SBH to a larger extent than that in the outer sublayer of MoS(2). (4) An increase in defect density increases the SBH. These findings indicate a large variation of SBH with the defect type, location, and concentration. We also compare our results with previously experimentally measured SBH for Au/MoS(2) contact and postulate possible reasons for the large differences among existing experimental measurements and between experimental measurements and theoretical predictions. The findings and insights revealed here may provide practical guidelines for modulation and optimization of SBH in Au/MoS(2) and similar heterojunctions via defect engineering.