Defect induced gap states in monolayer MoS2 control the Schottky barriers of Pt-mMoS2 interfaces

Abstract

Vacancies can significantly affect the performance of monolayer MoS2 (mMoS2) nanodevices because defect induced gap states can introduce large Schottky barriers at Pt-mMoS2 interfaces. Effects of adsorbed gases at S-vacancies on the defect induced gap states and Schottky barriers of Pt-mMoS2 interfaces have been studied by first-principles calculations. The defect induced gap states are occupied (unoccupied) ones when electron-rich (electron-poor) gases adsorb at S-vacancies. The occupied gap states in mMoS2 result in n-type Schottky barriers, whereas unoccupied gap states cause p-type Schottky barriers. Moreover, both the n-type and p-type Schottky barriers of Pt-mMoS2 interfaces decrease when the gap states are closer to the valence bands of mMoS2 because the gap states determine the direction and the amount of charge transfer at interfaces. The n-type and p-type Schottky barriers of Pt-mMoS2 interfaces are reduced to 0.36 and 0 eV by adsorbing high concentrations Cl2 and CO, respectively. Furthermore, adsorbing electron-poor gases (CO and NO) at S-vacancies change the n-type Pt-mMoS2 interfaces to p-type ones. These findings provide guidance to develop approaches to design high performance metal-mMoS2 interfaces with low Schottky barriers.