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Structural and optical properties of visible active photocatalytic WO3 thin films prepared by reactive dc magnetron sputtering

Published online by Cambridge University Press:  05 December 2012

Malin B. Johansson ,
Gunnar A. Niklasson  and
Lars Österlund
Malin B. Johansson*
Affiliation:
Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala, Sweden
Gunnar A. Niklasson
Affiliation:
Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala, Sweden
Lars Österlund*
Affiliation:
Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, SE-751 21 Uppsala, Sweden
*
a)Address all correspondence to these authors. e-mail: malin.johansson@angstrom.uu.se
b)e-mail: lars.osterlund@angstrom.uu.se
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Abstract

Nanostructured tungsten trioxide films were prepared by reactive dc magnetron sputtering at different working pressures Ptot = 1–4 Pa. The films were characterized by scanning electron microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, Raman spectroscopy, and ultraviolet–visible spectrophotometry. The films were found to exhibit predominantly monoclinic structures and have similar band gap, Eg ≈ 2.8 eV, with a pronounced Urbach tail extending down to 2.5 eV. At low Ptot, strained film structures formed, which were slightly reduced and showed polaron absorption in the near-infrared region. The photodegradation rate of stearic acid was found to correlate with the stoichiometry and polaron absorption. This is explained by a recombination mechanism, whereby photoexcited electron–hole pairs recombine with polaron states in the band gap. The quantum yield decreased by 50% for photon energies close to Eg due to photoexcitations to band gap states lying below the O2affinity level.

Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 24 , 28 December 2012 , pp. 3130 - 3140
Copyright
Copyright © Materials Research Society 2012

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