Abstrakt
We report on the preparation and characterization of high surface area, supported nanoporous tungsten oxide films prepared under different conditions on polished polycrystalline Ta and Pt(111) substrates via direct sublimation of monodispersed gas phase clusters of cyclic (WO3)(3). Scanning electron microscopy and transmission electron microscopy were used to investigate the film morphology on a nanometer scale.
The films consist of arrays of separated filaments that are amorphous. The chemical composition and the thermal stability of the films were investigated by means of X-ray photoelectron spectroscopy.
The surface area and the distribution of binding sites on the films were measured as functions of growth temperature, deposition angle, and annealing conditions using temperature-programmed desorption of Kr. Films deposited at 20 K and at an incident angle of 65 degrees from the substrate normal display the greatest specific surface area of similar to 560 m(2)/g.