SELECTIVELY C-13-ENRICHED DIAMOND FILMS STUDIED BY NUCLEAR-MAGNETIC-RESONANCE

The quality of hot-filament chemical-vapor-deposited diamond films has been quantitatively assessed by H-1 and C-13 nuclear-magnetic-resonance (NMR) spectroscopy. As the carbon mole fraction increases from 0.053 to 0.074 in the gas phase, film quality in terms of sp2 carbon content, bonding disorder, and spin-lattice relaxation times deteriorates, in agreement with the qualitative results of Raman spectroscopy and scanning electron microscopy. Selective isotopic labeling of the acetone reactant and subsequent C-13 NMR analysis shows that the carbonyl carbon of acetone is incorporated into the growing diamond films. Secondary-ion mass spectroscopy reveals that heterogeneous exchange reactions, involving the carbonyl carbon at the tantalum filament, are responsible for this phenomena.