Tuning Conductivity Type in Monolayer WS2 and MoS2 by Sulfur Vacancies

TL;DR

This study demonstrates that sulfur vacancies in monolayer WS2 and MoS2 can be used to switch their conductivity type between n-type and p-type by controlling vacancy density, offering a new approach for electronic device engineering.

Contribution

The paper provides a systematic first-principles analysis showing sulfur vacancies can tune the conductivity type of monolayer WS2 and MoS2, an alternative to doping.

Findings

Sulfur vacancies can switch WS2 and MoS2 from n-type to p-type and vice versa.

Vacancy density thresholds determine the semiconductor's charge carrier character.

Vacancy engineering offers a new method for tuning 2D TMDC electronic properties.

Abstract

While n-type semiconductor behavior appears to be more common in as-prepared two-dimensional (2D) transition metal dichalcogenides (TMDCs), substitutional doping with acceptor atoms is typically required to tune the conductivity to p-type in order to facilitate their potential application in different devices. Here, we report a systematic study on the equivalent electrical "doping" effect of - single sulfur vacancies (V1S) in monolayer WS2 and MoS2 by studying the interface interaction of WS2-Au and MoS2-Au contacts. Based on our first principles calculations, we found that the V1S can significantly alter the semiconductor behavior of both monolayer WS2 and MoS2 so that they can exhibit the character of electron acceptor (p-type) as well as electron donor (n-type) when they are contacted with gold. For relatively low V1S densities (approximately < 7% for MoS2 and < 3% for WS2), the monolayer TMDC serves as electron acceptor. As the V1S density increases beyond the threshold densities, the MoS2 and WS2 play the role of electron donor. The significant impact V1S can have on monolayer WS2 and MoS2 may be useful for engineering its electrical behavior and offers an alternative way to tune the semiconductor TMDCs to exhibit either n-type or p-type behavior.