Graphite-layer formation at a diamond (111) surface step

Nitridation of diamond(111) surface by density functional theory

Density functional theory was employed to examine the adsorption and thermal evolution of nitrogen species on diamond(111) impacted by microwave N2 plasma. On bare domains of diamond, as represented by the models of C(111)-2 × 1 and graphite-like C(111), N2(ad) is identified as the major surface species; the desorption of N2(ad) proceeds on both models via a concerted process of breaking two C-N bonds. By contrast, there is evidence of the formation of (NH)2(ad) via the insertion reaction of microwave N2 plasma on hydrogenated domains of diamond, as represented by the models of C(111)-2 × 1-H and C(111)-1 × 1-H. Interestingly, contrasting dynamics of desorption of (NH)2(ad) are presented on these two models, that is, via sequential breaking of two C-N bonds on C(111)-2 × 1-H and via concerted breaking of both C-N bonds on C(111)-1 × 1-H. Our results demonstrate that the observed diversity of surface nitrogen species in composition, bonding, vibration, and desorption in prior experiments is linked to domains of a variety of surface terminations and reconstructions on diamond(111).

Relationship of Processing Conditions to Growth Rate and Quality of Diamond Grown by Chemical Vapor Deposition

Diamond quality is strongly coupled to growth rate. Incorporation of nondiamond (sp2) carbon and morphological instabilities both increase with increasing growth rates. The intersection of twins with the growth surface produces re-entrant corners that enhance growth in the plane of the twin. Morphology and the development of texture both depend on substrate temperature and methane concentration and hence on growth rate. Experimental evidence and modeling results that relate growth rates and quality to controllable process parameters are reviewed.

Coexistence Of Two Carbon Phases At Grain Boundaries In Polycrystalline Diamond

Energies and structures for two models of <001> tilt grain boundaries in diamond have been calculated using a many-body empirical bond-order potential. The first model contains all four-fold coordinate atoms. The second model is a two-phase system in which a graphitic region connects the diamond grains. At selected misorientation angles we predict that the two-phase structures are energetically competitive with the sp 3 bonded structures when the width of the graphitic regions exceed 10–15Å.