STRUCTURE OF THIN DIAMOND FILMS - A H-1 AND C-13 NMR-STUDY

The H-1 and C-13 nuclear magnetic resonance (NMR) of thin diamond film s deposited from naturally abundant (1.1 at. %) as well as 50% and 100 % C-13-enriched CH4 heavily diluted in H-2 is described and discussed. Less than 0.6 at. % of hydrogen is found in the films which contain c rystallites up to approximately 15 mum across. The H-1 NMR consists of a broad 50-65-kHz-wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and is found not to be intrinsic to th e diamond structure. The C-13 NMR demonstrates that >99.5% of the C at oms reside in a quaternary diamondlike configuration. H-1-C-13 cross-p olarization measurement indicates that, at the very least, the majorit y of C-13 nuclei cross polarized by H-1, i.e., within three bond dista nces from a H-1 at a crystallite surface, reside in sp3 diamondlike co ordinated sites. The C-13 relaxation rates of the films are four order s of magnitude faster than that of natural diamond and believed to be due to C-13 spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of the measured relaxation rates indicates th at within the C-13 spin-diffusion length of square-root/DT1c approxima tely 0.05 mum, these centers are uniformly distributed in the diamond crystallites. The possibility that the dangling bonds are located at i nternal nanovoid surfaces is discussed.