Effect of substrate temperature on structural, electrical and optical properties of sprayed tin oxide (SnO2) thin films

The thin films of undoped tin oxide (SnO2) were deposited onto the amorphous glass substrates using a pneumatic spray pyrolysis technique (SPT). The films were deposited at various substrate temperatures ranging from 300 to 500 °C in steps of 50 °C. The effect of substrate temperature on structural, electrical and optical properties was studied. The thermal behavior of the precursor SnCl4·5H2O is described in the results of thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). Infrared (IR) spectroscopic studies reveal that the strong vibration band characteristic of SnO2 stretching is present around 620 cm−1. The Raman spectrum of SnO2 films indicated bonding between Sn and O2 at 580 cm−1. The X-ray diffraction study showed that all the films were polycrystalline with major reflex along (110) plane, manifested with amelioration of grain size at an elevated substrate temperature. The films deposited at 450 °C exhibited lowest resistivity (0.7 Ω cm) and consequently highest n-type conductivity among all the samples. The direct band gap energy was found to vary from 3.62 to 3.87 eV and transmittance at 630 nm varies from 73 to 85% with a rise in substrate temperature.