POLARIMETRY OF INHOMOGENEOUS FILMS OF ANISOTROPIC CRYSTALLITES - BIREFRINGENCE IN BATIO3 THIN-FILMS

We describe a polarimetric investigation of an inhomogeneous film of a nisotropic crystallites, for which the crystallite size cannot be reso lved by the polarimeter. We present a model of the film as a collectio n of stacks of randomly selected linear wave plates and present a simu lation of the polarimeter output with the model film as the specimen. We analyze the simulation results in terms of a stopped random walk on the Poincare sphere. The simulation results are sensitive to the spat ial resolution of the polarimeter, crystallite size, film thickness, a nd the presence of isotropic phases. When all but one variable can be determined independently, the model can be used to estimate the remain ing variable. The results reproduce linear-birefringence-type measurem ents on polycrystalline BaTiO3 thin films. The relative amount of isot ropic (cubic and amorphous) to tetragonal phase in two BaTiO3 films is estimated.