Tuning the Conductivity Type in Monolayer WS<sub>2</sub> and MoS<sub>2</sub> by Sulfur Vacancies
Jing Yang, Fabio Bussolotti, Hiroyo Kawai, Kuan Eng Johnson Goh
Abstract
While n ‐type behavior appears to be more common in as‐prepared two‐dimensional (2D) transition metal dichalcogenides (TMDCs), substitutional doping with electron accepting atoms is typically required to tune the conductivity to p ‐type in order to facilitate their potential application in different devices. Herein, a systematic study is reported on the equivalent electrical “doping” effect of single sulfur vacancies (V 1S ) in monolayer WS 2 and MoS 2 by studying the interface interaction of WS 2 –Au and MoS 2 –Au contacts. Based on the first principles calculations, it is found that the V 1S can significantly alter the semiconductor behavior of both monolayer WS 2 and MoS 2 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 V 1S densities (approximately <7% for MoS 2 and <3% for WS 2 ), the monolayer TMDC serves as electron acceptor. As the V 1S density increases beyond the threshold densities, the MoS 2 and WS 2 play the role of electron donor. The significant impact V 1S can have on monolayer WS 2 and MoS 2 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.