Gasochromic devices consisting of tungsten oxide, covered by a platinum catalyst thin film were produced by reactive DC magnetron sputtering. The influence of the deposition parameters on their properties was studied. The film stoichiometry was investigated by in situ XPS analysis and the microstructure by SEM analysis. Those two features were correlated to both oxygen partial pressure and total pressure during deposition. The optical efficiency of the films is discussed as a function of stoichiometry, microstructure, and deposition parameters. (c) 2005 Elsevier B.V. All rights reserved.