OPTICAL OSCILLATOR-STRENGTHS AND QUANTUM-MECHANICS MATRIX-ELEMENTS OFWO(3) POLYCRYSTALLINE THIN-FILMS

Polycrystalline films of WO3 were prepared by chemical vapour depositi on techniques. Optical reflection and transmission and mass densities of these films were measured. The optical properties of WO3 films are discussed in terms of the single average excitation energy, E0, the no rmalized coordinate matrix element, x2, the normalized macroscopic osc illator strength, f, and the bond packing factor, B. With the aid of t he effective medium theory, it is shown that in inhomogeneous WO3 film s these properties are equally related to the microstructure, i.e., th e volume fractions of crystalline, of amorphous material and of voids contained in the film. In general, the presence of voids in the film t ends to increase E0 and to decrease x2, f and B while all the above pa rameters decrease with increasing fraction of amorphous material. In o rder to support the theoretical conclusions, the experimentally measur ed properties of the stoichiometric and inhomogeneous films taking int o account only microstructure modifications are calculated and compare d with the data.