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Sensors 2005, 5(12), 594-603; doi:10.3390/s5120594

Photo-Induced Unpinning of Fermi Level in WO3

1,* , 1
, 3
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 and 4
1 Department of Physics University of Ferrara, Via Saragat 1c, 44100 Ferrara, Italy 2 INFN Section of Ferrara, Italy 3 Chemistry and Physics Department, Brescia, Italy 4 University of Wales Swansea, Swansea, UK
* Author to whom correspondence should be addressed.
Received: 6 October 2005 / Accepted: 19 December 2005 / Published: 20 December 2005
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Atomic force and high resolution scanning tunneling analyses were carried out onnanostructured WO3 films. It turned out that the band gap measured by scanning tunnelingspectroscopy at surface is lower than the band gap reported in the literature. This effect isattributed to the high density of surface states in this material, which allows tunneling intothese states. Such a high density of surface states pins the Fermi level resulting in modestsurface activity at room temperature. Photo activation of WO3 results in unpinning of theFermi level and thereby in higher chemical activity at surface.
Keywords: Scanning tunneling spectroscopy; pinning of Fermi level; chemoresistivity. Scanning tunneling spectroscopy; pinning of Fermi level; chemoresistivity.
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Malagù, C.; Carotta, M.C.; Comini, E.; Faglia, G.; Giberti, A.; Guidi, V.; Maffeis, T.G.; Martinelli, G.; Sberveglieri, G.; Wilks, S.P. Photo-Induced Unpinning of Fermi Level in WO3. Sensors 2005, 5, 594-603.

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