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 using 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 increased the growth parameter alpha, and for the conditions investigated [100] 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 the films became amorphous. For low levels (<5 ppt) the luminescence signal in the Raman spectra increased steadily with nitrogen addition, while the features associated with sp(2) and sp(3) bonded carbon were unchanged. Comparisons with natural diamond and hot-filament grown material demonstrate that nitrogen is a significant impurity in our acetylene source. Equilibrium calculations showed that NO and atomic nitrogen were the two dominant products that may be responsible for the observed changes in morphology and Raman spectra. (C) 1998 Elsevier Science S.A.