Chemical vapor deposition diamond nucleation induced by sp2 carbon on unscratched silicon

Abstract

Chemical vapor deposition (CVD) diamond nucleation is enhanced on most substrates by scratching with diamond grit prior to growth. The damage induced by such scratching makes this an unsuitable technique for many applications, and sheds little light on fundamental nucleation mechanisms, since the bulk of the crystals on such substrates probably grow homoepitaxially on diamond fragments embedded in the substrate during scratching. In this paper, we describe recent results in which unscratched silicon substrates overlaid with carbon fibers undergo very rapid and heavy CVD diamond nucleation when exposed to CVD diamond growth conditions. Exposure of such fiber-treated substrates to high temperature in an ultrahigh vacuum induces the formation of etch pits and trails of particulate debris which are extremely efficient diamond nucleators. Both the pits and the debris are carbon rich, and thus satisfy two criteria for “spontaneous”, i.e. non-epitaxial growth; (1) carbon saturation of the substrate surface, and (2) the presence of high-energy edge sites. The specific relationships between these characteristics and CVD diamond nucleation are discussed.