Abstract

Photoinduced structural changes in molecular semicrystalline ${\mathrm{As}}_{4}{\mathrm{Se}}_{3}$ 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 ${\mathrm{As}}_{4}{\mathrm{Se}}_{3}$ 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.

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