Reduction of Fermi level pinning at Au–MoS2 interfaces by atomic passivation on Au surface

Abstract

Monolayer molybdenum disulfide (MoS2), which is a semiconducting material with direct band gap of ∼1.8 eV, has drawn much attention for application in field effect transistors (FETs). In this connection, it is very important to understand the Fermi level pinning (FLP) which occurs at metal–semiconductor interfaces. It is known that MoS2 has an n-type contact with Au, which is a high work function metal, representing the strong FLP at Au–MoS2 interfaces. However, such FLP can obstruct the attainment of high performance of field effect devices. In this study, we investigate the reduction of FLP at Au–MoS2 interfaces by atomic passivation on Au(111) using first-principles calculations. To reduce the FLP at Au–MoS2 interfaces, we consider sulfur, oxygen, nitrogen, fluorine, and hydrogen atoms that can passivate the surface of Au(111). Calculations show that passivating atoms prevent the direct contact between Au(111) and MoS2, and thus FLP at Au–MoS2 interfaces is reduced by weak interaction between atom-passivated Au(111) and MoS2. Especially, FLP is greatly reduced at sulfur-passivated Au–MoS2 interfaces with the smallest binding energy. Furthermore, fluorine-passivated Au(111) can form ohmic contact with MoS2, representing almost zero Schottky barrier height (SBH). We suggest that SBH can be controlled depending on the passivating atoms on Au(111).