Effect of growth parameters on defect structure and optical properties of ultrathin SnO2 films

Tin oxide films with thicknesses in the range from 5 to 110 nm have been deposited by reactive dc magnetron sputtering of Sn in Ar + O plasma at a low working pressure of 1.0× 10−3 Torr on glass substrates at different temperatures (150–400 °C). The effect of deposition time, substrate temperature, and oxygen partial pressure on surface morphology, crystallographic structure, optical properties, and photoluminescence characteristics of SnO2 films has been studied and correlated with their defect structure. The structural transformation from nanocrystalline to polycrystalline of thicker films >40 nm and films were grown at higher temperature is explained based on adatom mobility and uniform substrate coverage. Based on photoluminescence characteristics and transmittance spectra, the 20 nm thick film exhibits the least defect structure and best electronic and optical behaviors. •Ultrathin SnO2 films (5–20 nm) are successfully grown by DC reactive sputtering.•Effect of scaling down film thickness (down to 5 nm) on physical properties.•Correlation between defect structure and optical properties.•Thinner films are much smoother than the thicker films.•Low structural defect concentration found in 10–40 nm films.