Photoinduced Effects for Amorphous Chalcogenide Semiconductors

Abstract

Chalcogenide glasses present diverse, fascinating photoinduced behavior when they are illuminated with photons. One of the thrust photoinduced phenomena in chalcogenide thin films is photodarkening (PD). In this phenomenon, the absorption coefficient increases, and the bandgap decreases. PD extensively occurs in thermally evaporated elemental S and Se and their binary compositions. The present article focuses on the PD effect on chalcogenide thin films, which causes structural and optical changes. The time evolution of change in the absorption coefficient and the optical band gap consists of a transient and metastable part. The kinetics of the optical changes is examined by using the photo-assisted site switching (PASS) model. PD result also changes the chemical environment and the structure of chalcogenide thin films. The extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), and Raman spectra have been analyzed to understand the fundamental chemical and atomistic changes during the process of PD.