Texture of (100) and (111) faces of annealed diamond crystal

Abstract

The synergistic combination of sp²- and sp³-hybridized carbons has multiple applications. Among various structural parameters, the texture of the interface layer in sp²-sp³ composites is perhaps one of the most important factor affecting their functional properties. In the present study, we investigated the early stages of graphitization of a synthetic diamond during high-vacuum annealing at 1250 °C. This was achieved using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and angle-resolved near-edge X-ray absorption fine structure spectroscopy in combination with density functional theory modeling. Our results showed that the texture of the graphitized layer can be controlled by the symmetry of the annealed diamond crystal face and by defect engineering. Specifically, arches merging with the diamond layer were formed on the (100) face, while nanographites were formed on the (111) face. In the latter case, the graphene sheets had a predominantly vertical orientation to the crystal face and could grew parallel in the etch pits. The stages of the structural evolution of diamond graphitization are discussed, including the rearrangement of the diamond surface, the detachment of carbon atoms, the formation of an amorphous sp² carbon layer, and its subsequent condensation into nanographite covalently bonded to the diamond surface.