Relation of absorption band edge of rutile films and their structure

Oriented films of TiO2 (rutile) were fabricated by oxidation of monocrystal films of pure titanium and those doped with nickel. Oxidation was performed in an atmosphere of pure oxygen or air. Oriented structures were obtained in both cases at the same temperatures. The dependence of optical absorption spectra from the grain (subgrain) size was established. Titanium oxide synthesized in air atmosphere is characterized by a shift in the absorption band edge to the low-energy side, whereas doping with nickel increases the band gap.