TIME-DEPENDENT EVOLUTION OF THE STRUCTURE AND CHEMICAL-BONDS IN DIAMOND-LIKE CARBON-FILMS GENERATED BY THE HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION METHOD

The chemical structure of inhomogeneous amorphous carbon films grown f or different lengths of time in a hot filament chemical vapour deposit ion reactor from a methane-hydrogen mixture has been investigated by e lectron energy loss spectroscopy (EELS) and Raman spectroscopy. The ch anges in EELS and Raman spectral shapes allowed us to monitor the time -dependent structural evolution of the films, from an amorphous lattic e with a noticeable fraction of sp3-bonded hydrogenated carbon atoms t o a prevalence of microcrystalline graphitic domains. The depth profil e of hydrogen in the grown film for 120 min has been measured by the H -1(N-15, alphagamma) C-12 nuclear reaction analysis technique. The low value of the hydrogen content (less than 4 at.%) is consistent with t he structure of this carbon film which has a density of 1.9 g cm-3. By the combined use of Rutherford backscattering spectrometry and nuclea r reaction analysis the mean carbon coverage thickness was found to be 22+/-5 nm. Secondary ion mass spectrometry measurements confirmed thi s conclusion.