Direct observation of laser-induced crystallization of a-C:H films |
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Authors: | L. C. Nistor J. Van Landuyt V. G. Ralchenko T. V. Kononenko E. D. Obraztsova V. E. Strelnitsky |
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Affiliation: | (1) EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium;(2) General Physics Institute, Russian Academy of Sciences, ul. Vavilova 38, 117942 Moscow, Russia;(3) Institute of Physics and Technology, ul. Akademicheskaya 1, 310108 Kharkov, Ukraine;(4) Present address: Institute of Atomic Physics, P.O. Box Mg. 6 Magurele, RO-76900 Bucharest, Romania |
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Abstract: | The post-growth modification of diamond-like amorphous hydrogenated carbon a-C:H films by laser treatment has been studied by transmission electron microscopy and Raman spectroscopy. a-C:H films grown on Si substrates by benzene decomposition in a rf glow discharge were irradiated with 15 ns pulses of a KrF-excimer laser with fluences in the range of E=50–700 mJ/cm2. At fluences below 100 mJ/cm2 an increase in the number of graphitic clusters and in their ordering was evidenced from Raman spectra, while the film structure remained amorphous according to electron microscopy and electron diffraction observations. At higher fluences the appearance of diamond particles of 2–7 nm size, embedded into the lower crystallized graphitic matrix, was observed and simultaneously a progressive growth of graphite nanocrystals with dimensions from 2 nm to 4 nm was deduced from Raman measurements. The maximum thickness of the crystallized surface layer (400 nm) and the degree of laser annealing are limited by the film ablation which starts at E>250 mJ/cm2. The laser-treated areas lose their chemical inertness. In particular, chemical etching in chromium acid becomes possible, which may be used for patterning the highly inert carbon films. |
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Keywords: | 61.80.Ba 61.16.Bg 78.30.– j |
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