On a possibility of the overgrowth of diamonds in the hydrocarbon atmosphere

The possibility to increase sizes of diamond crystals at least 25 $\mu$m by means of their annealing at a temperature of 1450 K in a hydrocarbon atmosphere has been studied. The initial diamond crystals are incorporated in the polyvinyl acetate layer on the surface of a silicon monocrystal and subjected to the annealing in methane atmosphere with low pressure in the presence of an external electric field with intensity up to 0.04 V/$\mu$m. Under these conditions the charged ions of methane dissociation products are accelerated and acquire the kinetic energy that is comparable with energy sufficient to form $sp^3$-hybride bonds, which can lead to an increase in the sizes of initial seed crystallites. The obtained substrates of a composite with a typical thickness not higher than 1.2 mm, which contain a joined diamond crystal in the carbon matrix, can be used as thermal conductive and electrical insulating spacers in devices for cooling items of electronic engineering.