Raman Spectra Calculation of Ordered-Vacancy Ga₂Se₃ Compounds; Origin of Anisotropy

Abstract

Polarized Raman spectra of ordered-vacancy Ga₂Se₃ were calculated using the sp³s^* tight-binding and vibration models. We found a large peak around 150 cm^-1 which originates from the breathing-like movement of Se atoms around the vacancy. Reflecting the localized nature of vibration and the dangling-bond direction of three-coordinated Se atoms, this peak shows large intensity and anisotropy; the intensity is large for the light polarization perpendicular to the vacancy array, in contrast to the anisotropy observed in the photo-absorption and luminescence. These results well explain the experiments.