OPTICAL-ABSORPTION AND ELECTRICAL-CONDUCTIVITY IN PLASMA-POLYMERIZED ORGANOISOTHIOCYANATE THIN-FILMS

Thin polymer films deposited from methyl-, n-propyl-, allyl-, and phenyl isothiocyanate in an radio frequency (RF, 13.56 MHz) plasma were characterized in terms of their optical absorption and electrical conductivity. The UV-VIS spectral data indicate for the presence of two optical gaps in the examined materials. Light absorption is related to the excitation of electrons with contribution of the localized states connected with molecules, which contain pi-bonds. The materials owing to their rather low conductivities (not exceeding 10(-11) S/m) can be classified as dielectrics. Thermal treatment of the films in nitrogen results in an increase of conductivity by three orders of magnitude. The polymer films reveal a substantial photoconductivity effect which appears to be dependent on the wavelength. The evaluated quantum efficiency values are 10(-5)-10(-4) el./quant.