Piezoelectric biaxial strain effects on the optical and photoluminescence spectra of 2D III–VI compound α-In2Se3 nanosheets

The controllable biaxial strain is experimentally imposed on α-In2Se3 nanosheets by an electromechanical device. A redshift of Raman spectra is observed from the nanosheets under the strain. The Gruneisen parameter is calculated to analyze the strain effect on the vibrational behavior. Photoluminescence shows a blueshift, which can reach up to 215 meV per 1% strain. Such tunability of optical characteristics observed from α-In2Se3 nanosheets is much higher than that from conventional semiconductors. The physical mechanism behind the observation is investigated, which is related to the variations in the energy band and photoexcited carriers under a piezoelectric field and laser power.