Tuning band structures and electronic properties of few-layer InSe by uniaxial strain

Atomically thin InSe joins the family of 2-dimensional materials recently with the advantage of high carrier mobility and layer-dependent bandgap. In this work, we engineer the band structures of few-layer InSe by uniaxial tensile strain. Prominent redshifts (90-100 meV per 1% strain) of photoluminescence peaks were observed in 4- to 8-layer samples. Density functional calculations well reproduce the observed strain effect and reveal that the shift rate decreases with increasing layer number for few-layer InSe, which can be understood based on the strain-induced change of the inter-layer interactions. In addition, resonant Raman spectroscopy was employed to study the vibrational properties of few-layer InSe. Sizable strain-induced redshifts of first order phonon modes and resonance effect were observed.