Origin of the n-type and p-type conductivity of MoS2 monolayers on a SiO2 substrate

Abstract

Ab initio density functional theory calculations are performed to study the electronic properties of a MoS 2 monolayer deposited over a SiO 2 substrate in the presence of interface impurities and defects. When MoS 2 is placed on a defect-free substrate, the oxide plays an insignificant role since the conduction band top and the valence band minimum of MoS 2 are located approximately in the middle of the SiO 2 band gap. However, if Na impurities and O dangling bonds are introduced at the SiO 2 surface, these lead to localized states, which modulate the conductivity of the MoS 2 monolayer from n -to p -type. Our results show that the conductive properties of MoS 2 deposited on SiO 2 are mainly determined by the detailed structure of the MoS 2 /SiO 2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS 2 -based devices