Strain engineered electronic structures and optical response of InS single crystal with negative Poisson's ratio

Abstract

In this study, we propose a novel strain engineering strategy to tune the electronic structures and optical properties of InS single crystal. InS single crystal has the negative Poisson's ratio character in the zigzag and armchair directions, and owns a direct band-gap of 3.027 eV at the static state. There is a transition from direct to indirect band gap for different deformation modes (uniaxial strains εx, εy, εz, and biaxial strain εy≡εz). For the compressive strain mode, the band gap of InS single crystal first increases and then decreases with the increasing strain, and it changes from a direct to an indirect band gap at a critical strain. However, for the tensile strain pattern, the band gap of InS single crystal monotonously decreases with the increasing strain. It also changes from a direct to an indirect band gap at a critical strain. The biaxial strain mode εy≡εz among all the stretching modes is the most advantageous way to realize the strain-dependent band gap engineering of InS single crystal. Thus, for all the considered strain modes, with the increasing strain, InS single crystal exhibits the enhanced absorption coefficient accompanied by the red-shifted optical absorption edge.