UV-vis and photoluminescent spectra of TiO₂ films

Abstract

TiO₂ fims have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0. 10 Pa.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(O₂)≥0.15 Pa, the band gap increased from 3.48 eV to 3.68eV for direct transition and from 3.27 eV to 3.34 eV 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 O₂ 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 2.63 eV and 2.41 eV, corresponding to 0.72 eV and 0.94 eV below the conduction band for a band gap of 3.35 eV, respectively. For the films sputtered at 0.10 Pa and 0.15 Pa, there was an energy band formed between 3.12 eV and 2.06 eV, corresponding to 0.23 eV and 1.29 eV below the conduction band.

Keywords

TiO₂ films / indirect transition / defect energy level / sputtering

References

[1] Duntriu D, Bally A R, Ballif C. Photocatalytic Degradation of Phenol by TiO₂ Thin Films Prepared by Sputtering. Applied Catalysis E: Environment, 2000, 25: 83-92.

[2] Hoffmann M R, Martin S T, Choi W. Environmental Application of Semiconductor Photocatalysis. Chem. Rev., 1995, 95: 69-96.

[3] Vancoppenolle V, Jouan P Y, Wautelet M, Dauchot J P, Hecq M. DC Magnetron Sputtering Deposition of TiO₂ Films in Argonoxygen Gas Mixtures: Theory and Experiments. Surface Coat. Technol., 1999, 116–119: 933-937.

[4] Babelon P, Dequiedt A S, Mostefa-sba H, Bourgeois S, Sibillot P, Sacilotti M. SEM and XPS Studies of Titanium Dioxide Thin Films Grown by MOCVD. Thin Solid Films, 1998, 332: 63-67.

[5] Mardare D, Tasca M, Delibas M, Rusu G I. On the Structural Properties and Optical Transmittance of TiO₂ Sputtered Thin Films. Applied Surface Science, 2000, 156: 200-206.

[6] Watanabe T, Nakajima A, Wang R, Mibabe M, Koizumi S. Photocatalytic Activity and Photoinduced Hydrophilicity of Titanium Dioxide Coated glass. Thin Solid Films, 1999, 351: 260-263.

[7] Takeda S, Suzuki S, Odaka H, Hosono H. Photocatalytic TiO₂ Thin Film Deposited onto Glass by DC Magnetron Sputtering. Thin Solid Films, 2001, 392: 338-344.

[8] Madhu P, Badrinarayanan S, Sastry Murali M. Nanocrystalline TiO₂ Studied by Optical, FTIR and X-ray Photoelectron Spectroscopy: Correlation to Presence of Surface Stress. Thin Solid Films, 2000, 358: 122-130.

[9] Meng L, Andritschky M, Santos M. The Effect of Substrate Temperature on the Properties of DC Reactive Magnetron Sputtered Titanium Oxide Films. Thin Solid Films, 1993, 223: 242-247.

[10] Gratzel Michael. Heterogeneous Photochemical Electron Transfer, 1989, Florida: CRC Press, Inc..

[11] Posadowski W M. Pulsed Magnetron Sputtering of Reactive Compounds. Thin Solid Films, 1999, 343–344: 85-89.