UV-Vis and Photoluminescent Spectra of TiO_2 Films

摘要

TiO_2 films have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0.10Pa to 0.65 Pa. The transmittance (UV-vis) and photoluminescence (PL) spectra of the films were recorded. The results of the UV-vis spectra show that the deposition rate of the films decreased at oxygen partial pressure P (O_2) >= 0.15 Pa, the band gap increased from 3.48eV to 3.68eV for direct transition and from 3.27eV to 3.34eV for indirect transition with increasing the oxygen partial pressure. The PL spectra show convincingly that the transition for films was indirect, and there were some oxygen defect energy levels at the band gap of the films. With increasing the O_2 partial pressure, the defect energy levels decreased. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63eV and 2.41eV, corresponding to 0.72eV and 0.94eV below the conduction band for a band gap of 3.35eV, respectively. For the films sputtered at 0.10Pa and 0.15 Pa, there was an energy band formed between 3.12eV and 2.06eV, corresponding to 0.23eV and 1.29eV below the conduction band.