The effect of pressure on optical properties of As₂S₃ glass

Optical experiments have been carried out on amorphous As₂S₃ under hydrostatic pressure. The absorption edge red-shifts very rapidly with pressure, with E_G dropping from 2.5 to 1.5 eV between 0 and 86 kbar. The near-infrared refractive index is similarly pressure-sensitive, increasing by 30% at 50 kbar. In contrast to the electronic spectra, the bond-stretching Raman band scarely shifts with P. These responses to pressure support the view that a-As₂S₃ is composed of discrete macromolecules. These data also show that the temperature dependences of E_G and n are dominated by the electron-phonon contribution.