Electronic Structure and Optical Properties of Monolayer $ReS_2$ with Defect Controlled by Strain Engineering

TL;DR

This study uses first-principles calculations to explore how strain engineering affects the electronic and optical properties of defected monolayer ReS2, revealing defect formation preferences and tunable optical responses.

Contribution

It provides new insights into defect formation, electronic structure transformation, and optical property tuning of monolayer ReS2 under strain, which was less understood before.

Findings

S4 defect is most likely to form among vacancies.

Strain induces a transition from direct to indirect band gap.

Optical reflection spectrum can be significantly tuned by external strain.

Abstract

By using first-principles calculations, we investigated the monolayer $ReS_2$ with vacancies under strain engineering, specifically focusing on its energy of formation, band gap, electron density of states, effective mass and optical properties. The calculated results disclose that S4 defect is more likely to form than other kinds of vacancies. Asymmetric deformation induced by strain makes its band structure transformation from direct band gap to indirect band gap. The analysis of the partial density of states indicates that the Re-d, Re-p and S-d orbitals are the major components of the defect states, being different from $MoS_2$, the defect states locate both above and below the Fermi level. Moreover, the effective mass was sensitive and anisotropic under the external strain. The reflection spectrum can be greatly tuned by the external strains, which indicates that the ReS2 monolayer has promising applications in nanoscale strain sensor and conductance-switch FETs.