CHARACTERIZATION OF HYDROGENATED AMORPHOUS-CARBON FILMS BY NUCLEAR-MAGNETIC-RESONANCE TECHNIQUES

Different nuclear magnetic resonance (NMR) methods have been used to i nvestigate the structure of hydrogenated amorphous carbon films. Besid es measuring the sp2-to-sp3 ratio by means of C-13 cross-polarization magic-angle spinning total suppression of spinning sidebands NMR we st udied the distribution of covalently bound hydrogen over Sp2- and sp3- type carbon atoms using dipolar dephasing techniques. The reliability of the dipolar dephasing measurements is discussed and the results are compared with the data derived from a simple statistical model. Moreo ver they are compared with previous IR spectroscopy measurements. H-1 combined rotation-and-multipulse NMR spectra are presented which do no t show resolved proton resonances in the case of as-deposited films bu t correspond in their line shape to the proton distribution measured w ith dipolar dephasing. Finally a few considerations concerning a refin ed structural model are presented.