Materials properties of out-of-plane heterostructures of MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, vibrational, and optical properties of out-of-plane heterostructures made from transition metal dichalcogenides, revealing tunable band gaps and optical behaviors.

Contribution

It provides new insights into the properties of MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$ heterostructures, including strain-induced band gap tuning and optical spectrum suppression.

Findings

MoS$_2$-WSe$_2$ is a direct band gap semiconductor.

WS$_2$-MoSe$_2$ is an indirect band gap semiconductor, tunable to direct with strain.

Interlayer charge transfer suppresses optical spectrum.

Abstract

Based on first-principles calculations, the materials properties (structural, electronic, vibrational, and optical properties) of out-of-plane heterostructures formed from the transiti on metal dichalcogenides, specifically MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$ were investigated. The heterostructures of MoS$_2$-WSe$_2$ and WS$_2$-MoSe$_2$ are found to be direct and ind irect band gap semiconductors, respectively. However, a direct band gap in the WS$_2$-MoSe$_2$ heterostructure can be achieved by applying compressive strain. Furthermore, the excitoni c peaks in both monolayer and bilayer heterostructures are calculated to understand the optical behavior of these systems. The suppression of the optical spectrum with respect to the c orresponding monolayers is due to interlayer charge transfer. The stability of the systems under study is confirmed by performing phonon spectrum calculations.