Effect of Microstructure of TiO₂ Thin Films on Optical Band Gap Energy

TiO₂ coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO₂ thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO₂ coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO₂ thin film, the band gap energy shifts from 3.4eV to 3.21eV. Moreover, other possible influence of the TiO₂ thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.