Controlling the Schottky barrier at MoS2|metal contacts by inserting a BN monolayer

TL;DR

This study demonstrates that inserting a BN monolayer between metal contacts and MoS2 can effectively control and reduce the Schottky barrier, facilitating better electronic contact in 2D semiconductor devices.

Contribution

It reveals how a BN monolayer disrupts metal-MoS2 interactions and aligns the Fermi level with MoS2 conduction band, enabling barrier control.

Findings

BN layer decreases Co and Ni work functions by ~2 eV

Fermi level pinned below conduction band for low work function metals

BN insertion restores MoS2 electronic structure and reduces Schottky barrier

Abstract

Making a metal contact to the two-dimensional semiconductor MoS2 without creating a Schottky barrier is a challenge. Using density functional calculations we show that, although the Schottky barrier for electrons obeys the Schottky-Mott rule for high work function ($\gtrsim 4.7$ eV) metals, the Fermi level is pinned at 0.1-0.3 eV below the conduction band edge of MoS2 for low work function metals, due to the metal-MoS2 interaction. Inserting a boron nitride (BN) monolayer between the metal and the MoS2 disrupts this interaction, and restores the MoS2 electronic structure. Moreover, a BN layer decreases the metal work function of Co and Ni by $\sim 2$ eV, and enables a line-up of the Fermi level with the MoS2 conduction band. Surface modification by adsorbing a single BN layer is a practical method to attain vanishing Schottky barrier heights.