NETWORK CONNECTIVITY AND STRUCTURAL DEFECTS IN A-C-H FILMS

In order to better understand the connectivity of the carbon network a nd the influence of hydrogen on the film microstructure in hydrogenate d amorphous carbon (a-C:H) films, we performed a comparative study of two series of a-C:H samples deposited by dissociation of methane in an r.f. discharge under different well-controlled conditions. From IR tr ansmission measurements we were able to accurately determine the vibra tional absorption spectra alpha(HBAR omega) over a large frequency ran ge (down to 500 cm(-1)). Special emphasis was put on the low frequency vibration modes in relation to the Raman spectra. The nature and dens ity of structural defects were also deduced from electron paramagnetic resonance experiments in order to obtain a more complete description of the samples. The results were correlated with the photoluminescence spectra.