Structural and optical properties and photoluminescence mechanism of fluorine-doped SnO2 films during the annealing process

F-doped SnO2 (SnOx:F) films deposited on a glass substrate by atmospheric pressure chemical vapor deposition (APCVD) were annealed at 600 °C for different times. The effects of annealing time on the structural, optical and photoluminescence (PL) properties of SnOx:F films were investigated. The results show that all the films have a polycrystalline cassiterite tetragonal crystal structure and exhibit obviously preferred orientations with (2 0 0) and (3 1 0) planes. The films annealed for 15 min possess the smallest particle sizes, of 94.95 nm, and a minimum root mean square roughness of 15.74 nm. The transmittances of all the films in the visible range can reach ∼80%. When the annealing time increases from 0 to 60 min, the optical band gap of SnOx:F films decreases from 3.91 to 3.87 eV. The room temperature PL spectra show weak UV emission, intense violet emission and broad and weak blue emission. The violet emission related to F substitutions and oxygen vacancies is composed of three PL subbands centered at 3.22, 3.03 and 2.81 eV. The photoemission position is observed to be independent of annealing time.