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Photoelectrochemical and structural properties of TiO2 and N-doped TiO2 thin films synthesized using pulsed direct current plasma-activated chemical vapor deposition

Randeniya, L. K. and Bendavid, A and Martin, P. J. and Preston, E. W. (2007) Photoelectrochemical and structural properties of TiO2 and N-doped TiO2 thin films synthesized using pulsed direct current plasma-activated chemical vapor deposition. JOURNAL OF PHYSICAL CHEMISTRY C, 111 (49). pp. 18334-18340.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp075938u

Abstract

Amorphous TiO2 thin films were synthesized using a pulsed direct cur-rent plasma deposition technique. The films were prepared in the discharges of Ar, Ar + O-2, and Ar + N-2. The original and annealed samples were characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, ultraviolet and visible spectroscopy (UV-vis), and electrochemistry. The presence of oxygen was found to be essential in the annealing medium for the formation of polycrystalline films. By optimizing the experimental conditions, we obtained TiO2 films that showed 80% incident photon conversion efficiency for splitting of water near 300 nm. Films containing up to 12 atom % N were obtained when mixtures of Ar and N-2 were used as the plasma source gas. Although there is evidence for the presence of Ti-N bonds in the amorphous film, the annealing in the presence of oxygen to obtain polycrystalline films led to decomposition of these bonds. The resulting polycrystalline films contained 1-2 atom % of N (XPS peak at 399.5 +/- 0.5 eV) and showed visible light absorption. However, in contrast to recent reports in the literature for powdered materials with similar XPS and UV-vis characteristics oxidation of water or formic acid could not be achieved using these films under visible light illumination. There is evidence that the holes generated in the occupied N 2p midgap levels are recombining efficiently at the carbon-impurity sites.

Item Type:Article
Subjects:Material Science > Nanofabrication processes and tools
Material Science > Nanostructured materials
Physical Science > Photonics
ID Code:1897
Deposited By:Farnush Anwar
Deposited On:16 Dec 2008 13:46
Last Modified:12 Feb 2009 17:23

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