THE INFLUENCE OF NITROGEN ADDITION ON THE MORPHOLOGY, GROWTH-RATE, AND RAMAN-SPECTRA OF COMBUSTION GROWN DIAMOND

The influence of intentional nitrogen addition on diamond deposition u sing a low pressure acetylene-oxygen flat flame was studied. The film morphology was assessed by scanning electron microscopy, growth rates by cross-section thickness measurements, and nitrogen incorporation by Raman spectroscopy. It was found that the addition of nitrogen increa sed the growth parameter alpha, and for the conditions investigated [1 00] textured films were obtained for nitrogen levels between three and five parts per thousand (ppt). It was found that there was no change in growth rate over the range 0-7 ppt N-2 addition. At higher levels t he films became amorphous. For low levels (<5 ppt) the luminescence si gnal in the Raman spectra increased steadily with nitrogen addition, w hile the features associated with sp(2) and sp(3) bonded carbon were u nchanged. Comparisons with natural diamond and hot-filament grown mate rial demonstrate that nitrogen is a significant impurity in our acetyl ene source. Equilibrium calculations showed that NO and atomic nitroge n were the two dominant products that may be responsible for the obser ved changes in morphology and Raman spectra. (C) 1998 Elsevier Science S.A.