INCORPORATION OF NITROGEN IN CHEMICAL-VAPOR-DEPOSITION DIAMOND

To study the incorporation of nitrogen, diamond films were prepared by chemical vapor deposition homoepitaxially on {100} and {111} oriented diamond substrates. 50 ppm of isotopic N-15(2) was added to the process gas. Nuclear reaction analysis was applied to determine quantitatively the concentration of incorporated N-15. The analysis is based on the detection of the 4.44 MeV gamma-radiation of the N-15(p,alpha(1) gamma)C-12 reaction. By a proper suppression of the gamma-background, a sensitivity of better than 0.5 ppm can be achieved. The measurements reveal a preferred incorporation of nitrogen into {111} growth sectors, the N-15 concentration in {111} growth sectors is by a factor of 3-4 larger than in the {100} growth sectors. The NIC ratios in the films were found to be in the ppm regime and four orders of magnitude below the N/C ratios in the gas phase. (C) 1995 American Institute of Physics.