Development of Sol Gel Derived Nanocrystalline TiO2 Thin Films via Indigenous Spin Coating Method

Abstract

In this paper, indigenous spin coater apparatus was fabricated and characterized by depositing transparent semiconducting thin films of TiO2 on glass substrates for 90 s at 6000 rpm followed by calcination procedures. The influence of the calcination temperature (400–800 °C) on electrical, optical, structural and photocatalytic properties of nano-crystalline titanium dioxide (TiO2) thin film were studied by four point probes, absorbance spectrum, X-ray diffraction (XRD), and photocatalytic activity test respectively. It has been investigated that the effect of conductivity increase may be caused by the increase of temperature. The XRD results showed that TiO2 thin film calcined at 400 °C was anatase, and further transformed into the rutile phase at higher calcination temperature. The crystallite size of TiO2 thin films was increased with increasing calcination temperature. Experimental results depicts that structural and electrical properties of the films are highly dependent on the growth temperature. It was observed that with increasing growth temperature, the average visible transmittance of the deposited films is enhanced and the residual stress in the thin films is obviously relaxed. The optical band gap energy decreases with increasing calcination temperature upto certain limit. Photocatalytic activity of thin films, evaluated by disintegration of methyl blue, methyl orange and RhB, was increased with variation in calcination temperature for a particular range. At 700 °C, the TiO2 thin film showed the highest photocatalytic activity due to better crystallization of TiO2 in the composite thin film.