Effects of substrate and annealing temperature on the microstructure, morphology, and optical properties of ZnS films were investigated. ZnS films were deposited on glass substrates by an electron beam evaporation system at different substrate temperatures and annealed at different temperatures in air. The structure and morphology of the film were studied by X-ray diffraction and atomic force microscopy. Transmittances of film were measured by spectrophotometer. Refractive indices and extinction coefficients were calculated from all transmittance data. Experimental results show that the as-deposited ZnS film exhibiting cubic structure, and the crystallinity is apparently improved with the increase of substrate temperature or annealing temperature. It is also found that film surface changes to ZnO after the film is annealed at 500 °C. The average surface grain size and root mean square surface roughness increase with the increase of annealing and substrate temperatures. Additionally, the increase of substrate temperature or annealing temperature will increase the pores in films, which results in the decrease of refractive indices and increase of extinction coefficients of the film.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.