Imperfections in amorphous chalcogenides. I. Electrically neutral defects in liquid sulfur and arsenic sulfides

The structures of chain ends in liquid S, As-S, and As-Ge-S were examined by use of ESR. They were found to be composed exclusively of radical species with electrically neutral dangling bonds. This means that formation of positively or negatively charged species is less probable in the liquids. The temperature dependence of the concentration of radical species followed the Arrhenius law, thus suggesting the existence of chemical equilibria between the normal bonding state and the dissociated states. S-S and As-As homopolar bonds were also detected by resonance Raman scattering even in the stoichiometric As₂{S}₃$ glass. These facts were interpreted in the following way: The initial reaction of bond fission in the liquids is thought to be radical cleavage of a normal bond. In the case of binary systems radical terminating reactions between the initial species give rise to the formation of homopolar bonds. Because of small enthalpy difference between the normal bond and the homopolar bonds, the concentration of homopolar bonds is expected to be high, which is consistent with the experimental observations.