D. Davazoglou et A. Donnadieu, OPTICAL OSCILLATOR-STRENGTHS AND QUANTUM-MECHANICS MATRIX-ELEMENTS OFWO(3) POLYCRYSTALLINE THIN-FILMS, Journal of non-crystalline solids, 169(1-2), 1994, pp. 64-71
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.