Temperature dependence of photoluminescence, Raman scattering, and transmittance spectra of anatase Ti1-xFexO2 nanocrystalline films

Anatase Ti1-xFexO2 (x=0, 1%, 2%) nanocrystalline films were prepared on quartz substrates by a facile nonhydrolytic sol-gel route. The structure and optical properties have been studied by X-ray diffraction (XRD), Raman scattering, transmittance spectra and temperature dependent photoluminescence (PL). The B1g, Eg and (A1g+B1g) modes of anatase phase TiO2 can be observed in Raman spectra. Dielectric functions have been extracted by fitting the transmittance spectra in the photon energy range of 0.5-6.5 eV with Adachi's model. The pure TiO2 film displays a strong broadening visible luminescence band; however, Fe-doped samples exhibit a very weak luminescence due to the increase of oxygen vacancy concentration in TiO2. With the temperature increases, the PL intensity decreases monotonously and there are five emission peaks for the pure sample in low temperatures, which could be attributed to oxygen vacancies, surface states and F+ center.