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 15N2 was added to the process gas. Nuclear reaction analysis was applied to determine quantitatively the concentration of incorporated 15N. The analysis is based on the detection of the 4.44 MeV gamma -radiation of the 15N(p, alpha 1 gamma )12C 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 15N concentration in (111) growth sectors is by a factor of 3-4 larger than in the (100) growth sectors. The N/C 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.