Strain-Tunable Electronic and Optical Properties of Monolayer Germanium Monosulfide: Ab-Initio Study

In the present work, we consider systematically the electronic and optical properties of two-dimensional monolayer germanium monosulfide (GeS) under uniaxial strains along armchair (AC-strain) and zigzag (ZZ-strain) directions. Our calculations show that, at the equilibrium state, the monolayer GeS is a semiconductor with an indirect band gap of 1.82 eV. While monolayer GeS is still an indirect band gap semiconductor under ZZ-strain, an indirect–direct energy gap transition can be found in the monolayer GeS when the AC-strain is applied. The optical spectra of the monolayer GeS have strong anisotropy in the investigated energy range from 0 eV to 8 eV. Based on optical properties, we believe that the monolayer GeS is a potential candidate for applications in energy conversion and optoelectronic technologies.