Optical properties and thermal stability of amorphous Ge–Sb–Se films

Ge–Sb–Se chalcogenide films with mean coordination number (MCN) from 2.27 to 2.66 were deposited by magnetron sputtering method. Annealing time dependent physical properties, such as refractive index, optical band gap, and thickness were investigated. It was found that, the Ge15Sb9.6Se75.4 film with MCN is 2.4 exhibits the smallest change ratio after long time (35 h) heat annealing in refractive index (<1%), optical band gap (<1%), and thickness (<3%). Together with the analysis of topological model, the component of Ge15Sb9.6Se75.4 with MCN is 2.4 can be considered as the best thermal stable film in this Ge–Sb–Se system. The film with larger refractive index of ~2.7 is very helpful to the application like chalcogenide waveguide.