AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP33
The Preparation and Chemical Reaction Kinetics of Microcrystalline Tungsten Bronze Thin Films with Peroxide and Nitrobenzene Solutions

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Surface Science Poster Session
Presenter: N.F. Materer, Oklahoma State University
Authors: N.F. Materer, Oklahoma State University
A. Apblett, Oklahoma State University
E.B. Kadossov, Oklahoma State University
K. Khan, Oklahoma State University
E.F. Shams, Oklahoma State University
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Microcrystalline tungsten bronze (HxWO3) thin films are prepared using wet chemical techniques or atomic hydrogen to reduce a tungsten oxide thin film. The oxide film is prepared by thermal oxidation of sputter deposited tungsten metal film on a quartz substrate. The crystallinity of these films is determined by X-ray diffraction. X-ray and ultra-violet photoelectron spectroscopy show that these films are indistinguishable from conventionally prepared tungsten bronze powders. In addition, platinum or silver metal is deposited on these films. The quartz support allows the total amount of incorporated hydrogen in the film to be quantified by monitoring the absorbance at 900 nm. This technique is utilized to study the oxidation kinetics of these films by either organic nitrides or peroxides. A satisfactory fit to a kinetic model that involves two simultaneous processes is obtained. The first one is the proton diffusion from the bulk of the film to its surface, and the second is a reaction of the surface proton with the oxidant. In the latter process it is assumed that the surface concentration of the oxidant is effectively constant. The proton diffusion coefficient and the activation energy for the reaction of tungsten bronze films with oxygen gas are also estimated. The addition of catalytic amounts of platinum or silver on the rate is also discussed.