The effects of point defect type, location, and density on the Schottky barrier height of Au/MoS2 heterojunction: a first-principles study

Using DFT calculations, we investigate the effects of the type, location, and density of point defects in monolayer MoS2 on electronic structures and Schottky barrier heights (SBH) of Au/MoS2 heterojunction. Three types of point defects in monolayer MoS2, 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 MoS2 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 MoS2, which is adjacent to Au substrate, increases the SBH to a larger extent than that in the outer sublayer of MoS2. (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/MoS2 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/MoS2 and similar heterojunctions via defect engineering.

Automated summary

In this study, the effects of different types, locations, and densities of point defects in monolayer MoS2 on the electronic structures and Schottky barrier heights (SBH) of Au/MoS2 heterojunction are investigated using DFT calculations. The results show that the SBH of monolayer MoS2 with defects is universally higher than that of the defect-free counterpart. Specifically, S divacancy and Mo-S antisite defects have a larger effect on increasing the SBH compared to S monovacancy. Defects located in the inner sublayer of MoS2 also have a larger impact on the SBH than those in the outer sublayer. Increasing defect density leads to a higher SBH. These findings provide practical guidelines for controlling and optimizing the SBH in Au/MoS2 heterojunctions through defect engineering.