APPLICATIONS OF DERIVATIVE LINE-SHAPE FITTING TO ELLIPSOMETRIC SPECTRA OF THIN-FILMS OF METAL-SUBSTITUTED PHTHALOCYANINES

Derivative line-shape fitting provides a method to reduce spectroscopic data to a set of mathematical parameters. This method is applied to the Q-band (around 2 eV) in dielectric function spectra of thin films (< 100 angstrom) of tetrasulfonated phthalocyanines measured with spectroscopic ellipsometry in the photon energy region 1.5-4.5 eV. It is found that by fitting line-shape functions to derived spectra it is possible to resolve an absorption band into individual resonances. In this work four different models for line-shapes have been used and criteria for choosing the best model are discussed. Applications, such as determination of energy positions of individual resonances in complex absorption bands and the dependence of these energies on film thickness and exposure to NO2/N2O4 (NOx), are presented. The possibility to do material identification by means of "fingerprinting" with the model parameters are also discussed.