Direct determination of the refraction index normal dispersion for thin films of 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA).

The improved approach for analysis of the thin film optical spectra exhibiting the interference fringes is presented. It is shown that, based on the positions of adjacent extrema, the interference order numbers can be easily identified allowing for determination of a model-free normal dispersion of the refraction coefficient provided the film thickness is known from an independent measurement. The usefulness of the presented method is illustrated by the analysis of the reflection spectra obtained for thin films of 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA) with various thicknesses determined with the atomic force microscopy (AFM). [ABSTRACT FROM AUTHOR]