Structural and optical studies of dielectric and metallic organic films

• Published in: Synthetic metals Vol. 84; no. 1; pp. 955 - 956
• Main Authors: Niko, A., Resel, R., Meghdadi, F., Turcu, R., Pruneanu, S., Leising, G.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 1997; Amsterdam Elsevier Science; New York, NY
• Subjects: Applied sciences; conjugated polymers; Exact sciences and technology; Infrared spectroscopy; optical absorption spectroscopy; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis; x-ray diffraction; Infrared spectroscopy; x-ray diffraction; conjugated polymers; optical absorption spectroscopy; Refraction index; Phenylene polymer; Experimental study; Oligomer; Thin film; Sulfonate; Conjugated polymer; Molecular orientation; Optical properties; Supramolecular structure; Doped polymer; Electrical conductor; Pyrrole polymer
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/S0379-6779(96)04228-2

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 metallic character; and thin films of para-Hexaphenyl (PHP) (an oligomer of poly( para-phenylene) which has been successfully used in blue light emitting diodes) produced by molecular beam deposition on glass substrates showing dielectric, semiconducting character. X-ray diffraction measurements reveal that both film types show a well ordered structure leading to anisotropy, but with a different chain orientation governed by the film growth mechanism. The PHP films grow with chains oriented near-normal to the substrate surface, while the chains in PPY films lie predominantly in the film plane. Refractive indices and absorption coefficients, calculated from optical reflectance and transmission spectra, exhibit a pronounced microstructure dependence, where the refractive indices of PPY in the infra-red region were strongly influenced by the doping methods.