Nitrogen addition during flame deposition of diamond: a study of nitrogen-enhanced growth, texturing and luminescence

The effect of nitrogen addition during flame deposition of diamond on the g rowth rate, morphology and spatial distribution of luminescent point defect s in the layers has been studied. For this, well-defined amounts of nitroge n were added to the acetylene and oxygen source gases. The samples were gro wn under conditions that are known to give diamond deposits with a central area which is unaffected by in-diffusion of nitrogen from the ambient. Cons equently, the observed features in this region must be totally ascribed to the deliberately added nitrogen. Upon nitrogen addition, the diamond growth rate in the central area of the deposits initially increases from 54 to 12 5 mu m/h, while at the same time a {001} texture develops. With further inc reasing nitrogen concentrations, the growth rate drops again while the diam ond crystallites in the layer start to deteriorate and become increasingly separated from each other. This results in a morphology which is usually ob served in an annulus around the central area of flame deposited diamond. Ph otoluminescence spectroscopy and cathodoluminescence topography reveal an i ncreasing incorporation of nitrogen as nitrogen-vacancy pairs and a loss of homogeneity in the central area of the diamond layers with increasing nitr ogen addition. Based on the results of the present study, a recipe is given for reproducible flame deposition by the use of a commercially available w elding torch and 99.6% pure acetylene. (C) 1999 Elsevier Science S.A. All r ights reserved.