STRUCTURAL AND OPTICAL STUDIES OF DIELECTRIC AND METALLIC ORGANIC FILMS

We report on x-ray structural and optical measurements on two types of organic materials: Polypyrrole (PPY) free-standing films produced by electrodeposition, and doped with p-toluenesulfonate, which exhibit me tallic character; and thin films of para-Hexaphenyl (PHP) (an oligomer of poly(para-phenylene) which has been successfully used in blue ligh t emitting diodes) produced by molecular beam deposition on glass subs trates showing dielectric, semiconducting character. X-ray diffraction measurements reveal that both film types show a well ordered structur e leading to anisotropy, but with a different chain orientation govern ed by the film growth mechanism. The PHP films grow with chains orient ed near-normal to the substrate surface, while the chains in PPY films lie predominantly in the film plane. Refractive indices and absorptio n coefficients, calculated from optical reflectance and transmission s pectra, exhibit a pronounced microstructure dependence, where the refr active indices of PPY in the infra-red region were strongly influenced by the doping methods.