Structural study of evaporated amorphousAs4S4films by x-ray-absorption fine structure

X-ray-absorption fine-structure data show that films prepared by flash evaporation from ${\mathrm{As}}_4$ ${\mathrm{S}}_4$ source material possess the cagelike ${\mathrm{As}}_4$ ${\mathrm{S}}_4$ molecular structure. These ${\mathrm{As}}_4$ ${\mathrm{S}}_4$ molecular structures, especially in the as-deposited film, are quite disordered as compared to those in c-${\mathrm{As}}_4$ ${\mathrm{S}}_4$. The ${\mathrm{As}}_4$ ${\mathrm{S}}_4$ molecules in the films are either randomly packed or at least have a much lower correlation than in c-${\mathrm{As}}_4$ ${\mathrm{S}}_4$. After photosoaking of the annealed films, the structure does not show any significant changes, which indicates any structural modifications after photosoaking in nonstoichiometric a-${\mathrm{As}}_{\mathit{x}}$ ${\mathrm{S}}_{1\mathrm{-}\mathit{x}}$ (0.4≤x≤0.5) are not directly related to the presence of ${\mathrm{As}}_4$ ${\mathrm{S}}_4$ molecules.