First observation of temperature dependent lightinduced response of Ge25As10Se65 thin films

TL;DR

This study reports the first observation of temperature-dependent light-induced responses in Ge25As10Se65 thin films, revealing photodarkening at low temperature and photobleaching at higher temperatures, with structural analysis supporting intrinsic changes.

Contribution

It demonstrates for the first time that Ge25As10Se65 chalcogenide glasses exhibit both photodarkening and photobleaching depending on temperature, challenging previous assumptions.

Findings

Photodarkening observed at 20 K

Photobleaching observed at 300 and 420 K

Structural analysis confirms intrinsic structural changes

Abstract

Ge rich ternary chalcogenide glasses (ChG) exhibit photobleaching (PB) when illuminated with bandgap light and such an effect is originating from the combined effect of intrinsic structural changes and photo-oxidation. In a sharp contradict to these previous observations, in this letter, we demonstrate for the first time that Ge rich Ge25As10Se65 ChG thin films exhibit photodarkening (PD) at 20 K and PB at 300 and 420 K for continuous illumination of ~ 3 hours. Strikingly, the temporal evolution of PD/PB show distinct characteristics at the temperatures of illumination and provide valuable information on the light induced structural changes. Further, structure specific far infrared (FIR) absorption measurements give direct evidence of different structural units involved in PD/PB at the contrasting temperatures. By comparing the lightinduced effects in vacuum and air, we conclude that intrinsic structural changes dominate over photo-oxidation in the observed PB in Ge25As10Se65 ChG thin films.