Mechanism of diamond formation on substrates abraded with a mixture of diamond and metal powders

In this work we report a study of CVD diamond formation on silicon substrates abraded with diamond, metal, and a mixture of diamond and metal powders. It was found that the deposited diamond particles density (DPD) obtained after abrasion with diamond powder can be enhanced by a few orders of magnitude by abrasion with a mixed metal/diamond slurry, whereas no enhancement was observed by use for surface abrasion a metal slurry alone. The residual diamond slurry density (RDSD) left on the substrates by abrasion with diamond slurry was measured from AFM images. It was observed that DPD followed by abrasion with pure diamond slurry does not exceed 10% of RDSD, whereas the presence of some metal residues alongside with diamond debris, may increase this value almost to 100%. The enhancement in DPD was in the order: virgin approximate to(Cu, Fe or Ti) < Di < (Cu + Di) < (Fe + Di) < (Ti + Di). These effects are explained qualitatively as follows. It is suggested that metal residues influence the rates of CVD diamond growth through facilitation of conversion of non-sp(3)-bonded carbon species to the sp(3)-one above the growing surface. This enhancement in sp(3)-bonded carbon surface concentration at the initial stages of deposition (before a stable substrate is formed) prevents the smallest diamond residues from being completely etched by atomic hydrogen.