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1756628 
Journal Article 
SRPES investigation of tungsten oxide in different oxidation states 
Masek, K; Libra, J; Skala, T; Cabala, M; Matolin, V; Chab, V; Prince, KC 
2006 
1 
Surface Science
ISSN: 0039-6028 
600 
8 
1624-1627 
WOS:000237206700013 
The microstructure and morphology of metal oxide films have
a large influence on the sensitivity, selectivity and stability of the gas sensors and catalysts.
Considering that the sensing properties of thin film sensors are strongly related to their
microstructures and to the exact stoichiometry of their surfaces, an accurate control of these
parameters is extremely important for the production of sensors with reproducible behavior. In
this paper, an influence of preparation and annealing conditions on the physical and chemical
properties of tungsten oxide thin film is investigated. Two types of samples having
polycrystalline structure were prepared by different methods (deposition under UHV conditions,
oxidation of metallic tungsten layer in air). The samples were reduced by heating in UHV at
different temperatures and/or by Ar ion bombardment. It was found that the stability of tungsten
oxide layer with respect to the treatment procedures depends strongly on the preparation
conditions of the sample. The reduction process is discussed in terms of different oxidation
states resolved in the W4f photoelectron spectrum. Easy reducibility of the tungsten oxide layer
prepared by vacuum deposition was found to be a consequence of its nano-crystalline structure.
(c) 2006 Elsevier B.V. All rights reserved. 
Tungsten oxide; photoelectron spectroscopy; oxidation state; reflection high-energy electron diffraction (RHEED)