Effects of thickness and atmospheric annealing on structural, electrical and optical properties of GZO thin films by spray pyrolysis

Gallium doped zinc oxide (GZO) films have been prepared on glass substrates by the spray pyrolysis (SP) technique. The effects of thickness and annealing in air and oxygen on structural, electrical and optical properties of GZO thin films were investigated. As-deposited films were found polycrystalline with hexagonal structure that showed compressive stress along the c-axis. The compressive stress was found to decrease by thickness and by annealing in air or oxygen. The best characteristics have been obtained after heat treatment in oxygen, where the highest carrier concentrations have been achieved and with visible transmittance of 85–70% and resistivity of 4.21–2.25 × 10−3 Ωcm with increasing thickness. The band gaps of oxygen annealed samples are found to have low values in comparison to air annealed and as deposited samples. The band gap dependence on the film thickness and annealing atmosphere is correlated to the shrinkage effect. Photoluminescence (PL) study was confirmed that broad visible emission in GZO films due to both the intrinsic traps and deep level vacancies.

► Polycrystalline GZO thin films were deposited by spray pyrolysis with various thicknesses.
► The physical properties of GZO films have been analyzed as a function of thickness.
► The GZO film properties were depends on the atmospheric annealing.
► The band gap dependence on film thickness and annealing atmosphere was associated with shrinkage effect.