Spin-coating of Ge₂₃Sb₇S₇₀ chalcogenide glass thin films

Thin film Ge₂₃Sb₇S₇₀ chalcogenide glass has emerged as an important material system for photonic applications due to its high non-linear refractive index. However, one of the challenges is developing low-cost methods to deposit films of glassy material while retaining glass stoichiometry and high film quality. In this paper, we demonstrate a spin-coating technique for the deposition of such films. The dissolution mechanisms of Ge₂₃Sb₇S₇₀ in different solvents are studied in order to select the optimal solvent for film deposition. We show that the use of amine-based solvents allow the deposition of stoichiometric films in contrast to alkaline solutions. Films with low surface roughness (RMS roughness <5 nm) and controlled thickness (100-600 nm) can be deposited from solutions. We also show that annealing the films in vacuum decreases the amount of residual solvent, the presence of which is expected to lead to variation in optical properties of the thin films.