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

TL;DR

This study uses ab-initio calculations to explore how interface impurities and defects at the MoS2/SiO2 boundary influence the monolayer's n- or p-type conductivity, highlighting substrate doping as a control method.

Contribution

It reveals the critical role of interface impurities and defects in determining MoS2's conductivity type on SiO2, providing insights for device engineering.

Findings

Na impurities induce n-type conductivity

O dangling bonds induce p-type conductivity

Interface structure controls electronic properties

Abstract

Ab-initio density functional theory calculations are performed to study the electronic properties of a MoS2 monolayer deposited over a SiO2 substrate in the presence of interface impurities and defects. When MoS2 is placed on a defect-free substrate the oxide plays an insignificant role, since the conduction band top and the valence band minimum of MoS2 are located approximately in the middle of the SiO2 band-gap. However, if Na impurities and O dangling bonds are introduced at the SiO2 surface, these lead to localized states, which modulate the conductivity of the MoS2 monolayer from n- to p-type. Our results show that the conductive properties of MoS2 deposited on SiO2 are mainly determined by the detailed structure of the MoS2 /SiO2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS2 -based devices.