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Thin carbon and carbon nitride films exhibit specific optical and mechanical properties which make them promising materials for integrated optics. For this purpose we have investigated the preparation and optical properties of carbon and carbon nitride (CNx) films deposited on silicon substrates. The contribution deals with the study and fabrication of planar optical waveguides on semiconductor (silicon) substrates by the method of Plasma Assisted Chemical Vapor Deposition (PACVD). This waveguide is a carbon or carbon nitride layer deposited in a PACVD apparatus on a layer of silicon oxide, which also provides optical shielding of the substrate and is prepared by the oxidation of a silicon substrate wafer. The carbon as well as carbon nitride layers were fabricated by the reaction of methane, methane and nitrogen or methane and ammonia, respectively, in the PACVD apparatus. The fabricated films were characterized by optical ellipsometry and standard mode spectroscopy at 633 nm. The attenuation of the best sample was less than 0.3 dB/cm. It was found that optical and mechanical properties of films fabricated on the positive and negative electrodes were substantially different. The films deposited on the negative electrode were harder and their refractive index was higher compared with those deposited on the negative electrode. The refractive index of the harder films ranged from 2.2 to 2.6, while for the softer films it ranged from 1 .6 to 1 .8. We proved that it is in principle possible to dope the deposited layers with erbium ionsso that the resulting structures can also be used as active waveguides.
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