Comparison of microstructure and electronic properties of TiO 2 thin films grown by different techniques

Thin films of TiO₂ were grown on alumina and silicon substrates through various deposition routes, namely, radio frequency sputtering, pulsed laser deposition and spray pyrolysis. The films were characterised using X-ray diffraction, Raman spectroscopy, scanning electron microscopy and ultraviolet-visible spectroscopy. The band gaps of the thin films were compared with respect to their morphology, phase structure and composition. The particle sizes obtained were in the range of 10–30 nm, and spherical or bead-like morphology was obtained depending on the processing route used. The band gaps showed an increase from 3·28 to 3·50 eV upon decrease in particle size, which correlated well with the theoretical studies. Nanoindentation studies performed on the films grown on Si showed higher hardness and modulus for radio frequency sputtering films compared to other techniques. The microstructurally tunable electronic properties can be exploited to derive specificity and sensitivity towards gas sensing.