Aging effect of diethanolamine derived precursor sol on TiO₂ films deposited at different annealing temperatures

A diethanolamine stabilized precursor sol has been utilized for studying the effect of sol aging and annealing temperature on key properties of TiO₂ films. X-ray diffraction investigations have shown increased crystallite size in the films as a function of both sol aging and the thermal treatment. Fourier transform infrared studies have elucidated that cleavage of the bond involving diethanolamine and the alkoxide in the films requires high temperature annealing treatment upon the use of aged sol for the deposition of the films. Multiple step chronoamperometry has shown the ion storage capacity of the films increases as a function of sol aging, with the highest extent of Li ion insertion being obtained for films produced from as-prepared and aged sols and subsequently annealed at, 300 and 350 °C, respectively. Films with excellent optical quality were obtained. Ellipsometry revealed that the refractive indices of the films vary from 1.67 to 2.02. The highest thickness obtained in these films was nearly 900 nm. The bandgaps of the films for both direct and indirect transitions decreased as a function of precursor sol’s aging. In addition, although the indirect bandgap values have shown a decrease with increasing annealing temperature, the direct bandgap values reveal a slight increase as a function of annealing temperature.