Microstructure, optical and photoelectron-chemical properties of TiO₂ microspheres prepared by hydrothermal method

Anatase TiO₂ microspheres have been prepared by hydrothermal method and the reaction concentrations of mix solution containing hydrofluoric acid (HF) and ammonium fluoride (NH₄F) are 0.1, 0.2, and 0.4 M, respectively. Microstructure, morphology, chemical composition, optical and photoelectron-chemical properties of the as-deposited thin films were investigated in detail. XRD analysis shows that the grain size of the microspheres increases with increasing the reaction concentration. The films deposited at 0.1 and 0.2 M are formed by wellfaceted, regular microspheres with the size of 2–3 μm. XPS measurement indicates that the atomic ratio of Ti:O is estimated to be 1:2.05 for the sample deposited at 0.2 M. The band gap is close to the standard values of anatase TiO₂ 3.2 eV as the reaction concentration increases. The photocurrent of TiO₂ film deposited for 0.1 M reaction concentration is around three times as strong as those for 0.2 and 0.4 M under the same illumination. Current results will help to synthesise desired TiO₂ films and expand its applications.