Largely tunable band structures of few-layer InSe by uniaxial strain

TL;DR

This study demonstrates that uniaxial tensile strain can effectively tune the band structures of few-layer InSe, significantly shifting its optical properties and revealing potential for flexible optoelectronic applications.

Contribution

First experimental demonstration of uniaxial strain tuning of band structures in few-layer InSe, supported by density functional calculations showing layer-dependent effects.

Findings

Optical gap shifts by 90-100 meV per 1% strain in 4-8 layer InSe

Strain effect decreases with increasing layer number

InSe's tunable properties make it suitable for flexible optoelectronic devices

Abstract

Due to the strong quantum confinement effect, few-layer {\gamma}-InSe exhibits a layer-dependent bandgap, spanning the visible and near infrared regions, and thus recently draws tremendous attention. As a two-dimensional material, the mechanical flexibility provides an additional tuning knob for the electronic structure. Here, for the first time, we engineer the band structures of few-layer and bulk-like InSe by uniaxial tensile strain, and observe salient shift of photoluminescence (PL) peaks. The shift rate of the optical gap is approximately 90-100 meV per 1% strain for 4- to 8-layer samples, which is much larger than that for the widely studied MoS2 monolayer. Density functional calculations well reproduce the observed layer-dependent bandgaps and the strain effect, and reveal that the shift rate decreases with increasing layer number for few-layer InSe. Our study demonstrates that InSe is a very versatile 2D electronic and optoelectronic material, which is suitable for tunable light emitters, photo-detectors and other optoelectronic devices.