Correlation between a.c. transport and electron spin resonance in amorphous Ge-S films alloyed with lead

Abstract

Although the a.c. loss in amorphous chalcogenides has been well interpreted in terms of a model of charged defects D ⁺ and D ⁻, there is no direct (experimental) evidence for this. It is demonstrated for the first time that the a.c. conductivity is related to electron spin resonance and light-induced electron spin resonance in amorphous Ge-S films alloyed with Pb, showing direct evidence for defect-related a.c. transport. Alloying with Pb may result in a decrease in network flexibility, and hence the number of neutral defects D⁰ (positive correlation energy; positive U) increases with increasing Pb content. This may be one of the reasons for the disappearance of photodarkening when a certain amount of Pb is introduced into the Ge-S system.