Synthesis of diamond from methane and nitrogen mixture

Abstract

We have found that diamond can be synthesized from a mixture of CH4 and N2 without adding any H2. This new synthesis is sharply different from the common practice of diamond growth by chemical vapor deposition, which uses a hydrogen-rich mixture of CH4 and H2. In this new approach, nitrogen becomes an active component of microwave plasma leading to diamond growth. Nitrogen participates in abstraction of hydrogen from the diamond surface. We hypothesize that formation of HCN is an indication of hydrogen abstraction that allows diamond to grow from CH4+N2 mixtures. As a consequence of surface processes, the crystal structure of the grown diamond is distorted. The sequence of tetrahedral layers is mixed (cubic and hexagonal) and it suffers from turbostatic disorder. Diamond films were characterized by x-ray diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy.

Ellipsometric investigation of nitrogen doped diamond thin films grown in microwave CH4/H2/N2 plasma enhanced chemical vapor deposition

“…These observations are in agreement with our previous findings. 9 Moreover, a similar trend was reported by Badzian et al 11 or Bohr et al…”

“…Nitrogen incorporation results in significant mechanical stress and increases the number of vacancy defects due to distortion of the diamond lattice. [9][10][11] Several articles were published on the influence of nitrogen on the growth rate and quality of diamond films. [10][11][12][13][14] These 15 experiments were done using gas mixtures of CH 4 /H 2 /N 2 in microwave plasma reactors.…”

Microwave Plasma Process for SiCN:H Thin Films Synthesis with Composition Varying from SiC:H to SiN:H in H2/N2/Ar/Hexamethyldisilazane Gas Mixture

“…Thus, C involved in these reactions is badly incorporated in the growing film as evidenced by the very low C-N bonding rate observed from XPS and FTIR thin films analysis (Figure 2 and 3a). Such reactions of nitrogen and carbon producing carbonitride volatile species have also been reported by some authors working on the synthesis of diamond in CH 4 /N 2 plasma [41] or on the etching of carbonaceous material by N 2 plasma. [42] On the other hand, N bonds to Si, forming species that participate to the thin film growth.…”

Spatial distributions of H, CN, and C2 in a diamond-growing oxyacetylene flame

“…The fact that the maxima in the horizontal CN profiles coincide with the annulus of enhanced growth (also found for other values of d [16]) therefore indicates that CN or a closely related species (only one or two reaction steps away) may be important in the diamond growth process in the annulus, regarding both the morphology and the local growth rate. The influence of CN (or a closely related species) on the growth rate may be explained by the possibilities of CN and HCN to abstract adsorbed hydrogen from the growing diamond surface [26,27]. The preferential formation of {100} facets parallel to the substrate in and close to the annulus of enhanced growth may also be related to the presence of CN or a closely related species, because similar morphologies have been observed upon nitrogen addition to flame and other diamond-growing CVD systems [26,[28][29][30][31][32], studies in which also the positive effect of nitrogen addition to the diamondgrowth rate is described.…”