Raman scattering and photodarkening of amorphous Ge1−XSX (0⩽X⩽0.62) films

Amorphous Ge1−XSX films with Ge-rich composition of 0⩽X⩽0.62 were prepared by the laser ablation method to investigate the effect of sulfur on optical properties. From Raman spectra, it is found that the structure changes gradually with composition X. The change of properties from tetrahedral to chalcogenide semiconductors was examined in terms of photodarkening phenomena. As X increased, the photodarkening effect began to be observed at X=0.2 and enhanced significantly at X=0.5.