Dependence of the Physical Properties of Titanium Dioxide (TiO2) Thin Films Grown by Sol-Gel (Spin-Coating) Process on Thickness

In this work, high transparent TiO 2 nano-crystallinethin films have been prepared by a simple sol–gel spin coating technique. The effects of number of layers on physical properties of TiO 2 thin films were studied by means X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis spectrophotometer, and four probes measurement. The XRD analysis confirms that TiO 2 has anatase phase structure with preferred orientation of (101) direction, while the crystallite size values varied with the number of layers in the range of 16–19 nm. The films exhibit high optical transparency (>70%), reaching a maximum of 85% in the visible region with the red-shifted absorption edge, suggesting the films optical gap energy decreases with increasing number of layers from 3.67 to 3.52 eV. However, the Fourier transform infrared (FTIR) reflectance spectra show the existence of functional groups and chemical bonding. The films electrical properties measurement indicated that the substantially enhancement in the resistivity with increasing the number of layers from 3.3 × 10 5 to 2.15 × 10 6 Ω.cm. This study indicates that TiO 2 films may be a potential candidate in technological applications as solar cells, photocatalysts and gas sensors due to its desired structural, optical and electrical properties.