Prolonged exposure to strongly absorbed light induces irreversible and reversible changes in the ac conductivity (${\sigma }_{\mathrm{ac}}$) of amorphous ${\mathrm{As}}_2$${\mathrm{S}}_3$ films. The irreversible change (decrease of ${\sigma }_{\mathrm{ac}}$) observed for as-deposited films is ascribed to photopolymerization. The reversible change (an increase of ${\sigma }_{\mathrm{ac}}$ after illumination and removal of change by annealing) is attributed to defect creation and annihilation.

• Received 24 August 1987

DOI:https://doi.org/10.1103/PhysRevB.36.7741