Structural and optical properties of SnO2 nano films by spin-coating method

In this work, tin oxide (SnO2) nano films were deposited on glass substrates with different water content using the sol-gel spin-coating method. SnO2 is a wide band gap semiconductor and it belongs to the class of transparent conductive oxides (TCO). The influence of the water content and the heat treatment temperature on the structural and optical properties of the thin films is characterized by X-ray diffractometer (XRD), scanning electron microscope, atomic force microscope, ultraviolet-visible spectrophotometer, and spectrophotometer. Crystallite size of nano SnO2 films was controlled by SnCl2:water ratios. The most significant characteristic of nano materials is the increase in surface area as particle size decreases. XRD studies showed that the formation of tetragonal rutil phase was initiated at an annealing temperature close to 450 °C. The activation energy of nano SnO2 films for particle growth was calculated. The film has an activation energy of 42.8 kJ/mol, and the optical band gap of 3.02-3.35 eV is proportional to the SnCl2:water ratio. The quantum size effect of nano particles was confirmed by the band gap energy shift, using ultraviolet-visible spectroscopy (UV-vis). SnO2 films have been considered as one of the most promising functional materials due to their wide direct band-gap, and excellent electrical and optical properties. Those properties of SnO2 films allow them to be used in electronic and optoelectronic devices like gas sensors, solar cells and lithium batteries etc.