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Article
Effects of annealing treatment on optical properties of anatase TiO 2 thin films
World Academy of Science, Engineering and Technology (2009)
Abstract

In this investigation, anatase TiO 2 thin films were grown by radio frequency magnetron sputtering on glass substrates at a high sputtering pressure and room temperature. The anatase films were then annealed at 300-600 °C in air for a period of 1 hour. To examine the structure and morphology of the films, X-ray diffraction (XRD) and atomic force microscopy (AFM) methods were used respectively. From X-ray diffraction patterns of the TiO 2 films, it was found that the as-deposited film showed some differences compared with the annealed films and the intensities of the peaks of the crystalline phase increased with the increase of annealing temperature. From AFM images, the distinct variations in the morphology of the thin films were also observed. The optical constants were characterized using the transmission spectra of the films obtained by UV-VIS-IR spectrophotometer. Besides, optical thickness of the film deposited at room temperature was calculated and cross-checked by taking a cross-sectional image through SEM. The optical band gaps were evaluated through Tauc model. It was observed that TiO 2 films produced at room temperatures exhibited high visible transmittance and transmittance decreased slightly with the increase of annealing temperatures. The films were found to be crystalline having anatase phase. The refractive index of the films was found from 2.31-2.35 in the visible range. The extinction coefficient was nearly zero in the visible range and was found to increase with annealing temperature. The allowed indirect optical band gap of the films was estimated to be in the range from 3.39 to 3.42 eV which showed a small variation. The allowed direct band gap was found to increase from 3.67 to 3.72 eV. The porosity was also found to decrease at a higher annealing temperature making the film compact and dense.

Keywords
  • Optical properties,
  • RF reactive sputtering,
  • Structural properties,
  • Surface morphology,
  • Titanium dioxide,
  • AFM image,
  • Anatase films,
  • Anatase phase,
  • Anatase TiO,
  • Annealed films,
  • Annealing temperatures,
  • Annealing treatments,
  • As-deposited films,
  • Cross sectional image,
  • Crystalline phase,
  • Direct band gap,
  • Extinction coefficients,
  • Glass substrates,
  • Optical thickness,
  • Radio frequency magnetron sputtering,
  • Room temperature,
  • SEM,
  • Small variations,
  • Sputtering pressures,
  • Structure and morphology,
  • Tauc model,
  • TiO,
  • Transmission spectrums,
  • Visible range,
  • Visible transmittance,
  • Annealing,
  • Atomic force microscopy,
  • Crystalline materials,
  • Diffraction,
  • Energy gap,
  • Holographic interferometry,
  • Light transmission,
  • Morphology,
  • Optical band gaps,
  • Optical constants,
  • Organic polymers Refractive index,
  • Thin films,
  • Titanium,
  • Titanium oxides,
  • X ray diffraction,
  • Optical films
Publication Date
2009
Citation Information
"Effects of annealing treatment on optical properties of anatase TiO 2 thin films" World Academy of Science, Engineering and Technology Vol. 40 (2009)
Available at: http://works.bepress.com/asmd_haseeb/25/