Evolution of the structure and properties of solution-based Ge23Sb7S70 thin films during heat treatment

Optical devices such as waveguides and resonators have typically been produced through standard vacuum deposition and photolithography techniques. Solution-derived chalcogenide films are presented as an alternative for devices not easily fabricated through these standard techniques; however, many details of the chemical processes involved in film deposition are still unknown. We present a detailed analysis of the formation of Ge23Sb7S70 films from solution: solvent removal was studied using in situ FTIR and UV–visible absorption spectroscopies during heat treatments at various temperatures, and the glass structure and glass–solvent interactions were studied through analysis of the far- and mid-IR regions, respectively. Correlations have been established between atomic-level structural aspects and macroscopic physical properties such as refractive index, band gap energies, and surface roughness.