Insight into the photoinduced phenomena in ternary Ge-Sb-Se sputtered thin films

The kinetics of photoinduced changes,namely,photobleaching and photodarkening in sputtered ternary GeSbSethin films,was studied.The study of time evolution of the absorption coefficientΔα(t)upon roomtemperature near-bandgap irradiation revealed several types of photoinduced effects.The as-deposited films exhibited a fast photodarkening followed by a dominative photobleaching process.Annealed thin films were found to undergo photodarkening only.The local structure studied by Raman scattering spectroscopy showed significant structural changes upon thermal annealing,which are presumably responsible for a transition from the photobleaching observed in as-deposited and reversible photodarkening in annealed thin films.Moreover,a transient photodarkening process was observed in both as-deposited and annealed thin films.The influence of the initial film thickness and laser optical intensity on the kinetics of photoinduced changes is discussed.