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Hydrogen in polycrystalline diamond. An infrared analysis.
Wasserstoff in polykristallinem Diamant. Eine Infrarot-Analyse
Hydrogen in polycrystalline diamond (PCD) films has been analysed by infrared spectroscopy. A series of differently prepared PCD films exhibiting considerable differences in the shape of the C-H stretch absorption band has been studied. The spectra are consistently explained by a superposition of lines from sphigh3 hybridized CHsub3, CHsub2 and CH groups. The corresponding vibrational frequencies coincide with those of amorphous hydrogenated carbon (a-C:H). Contributions of sphigh2 hybridized CHsubn groups are found to be less than 10 %. In addition to the known a-C:H lines a diamond specific C-H vibration at 2822 cmhigh-1 has been observed for the first time in PCD. It is shown that hydrogen is incorporated in noncrystalline and defective regions of the PCD film, i.e. at grain boundaries and dislocations. For decreasing grain size (increasing defect content) the hydrogen concentration increases. In many samples the sphigh3 hybridized CHsub2 group is dominant (up to 69 %).Within a ser ies, where the hydrocarbon concentration in the feed gas was varied, samples with high abundances of sphigh3CHsub3 (49 %) and sphigh3CH (28 %) have been prepared.