Photoinduced volume change in arsenic chalcogenides by band-gap light

Photoinduced structural changes in molecular semicrystalline As4Se3 films have been characterized by extended x-ray absorption fine structure and x-ray diffraction under in situ band-gap laser illumination. Transient and permanent changes in the local and long-range structure have been determined quantitatively. In contrast to fully amorphous arsenic selenide films, a photoinduced contraction has been observed in semicrystalline As4Se3 films. A comprehensive phenomenological model is proposed for the photoinduced volume change in As-based chalcogenides. This model is based on two competing processes viz. intermolecular interaction through Coulombic repulsive force that results in photoexpansion, and cross-linking of molecular units through bond switching that causes photocontraction. A guideline is presented for selecting chalcogenide glass composition with specific photoinduced volume change characteristics.