A. Rudenko

Formation of diamond nuclei under the growth of films and crystals from the gas phase

Abstract Kinetic conditions of equilibrium (critical) formation of diamond nuclei and non-equilibrium growth of macroscopic diamond crystals and films by the polycondensation of small carbon-containing molecules are considered. There are essential distinctions in macrokinetic conditions for formation of nuclei and macrocrystal growth when the same microkinetic conditions of diamond substance formation occur. The diamond macrocrystals can grow only under conditions of non-equilibrium in open catalytic systems, but nuclei can be formed in closed ones until the establishment of the equilibrium. A method of estimating equilibrium nucleus parameters is proposed, depending on the conditions of their formation under a polycondensation process. According to these calculations, the equilibrium nuclei are thin epitaxial films having a ratio of the thickness to the diameter equal to 2 × 10−4. The thickness of the nuclei decreases by 10–30 times (depending on the nature of the polycondensation process) when the temperature of this process increases from 400 to 1000 K.

To the Question of the Diamond Nuclei’s Formation from the Gas Phase

One can’t think that the formation of polymorphic carbon forms (diamond, graphite, charbon) having different chemical nature of carbon-carbon bonds is a simple physical crystallization of carbon atoms. Undoubtedly in this case chemical factors have a decisive importance and the above-mentioned polymorphic forms of carbon are products in different chemical reactions. As it has been shown in [1,2] they are condensing products which form in polycondesation processes of the type

STUDY OF CHEMICAL MODIFICATION OF DIAMOND SURFACE BY THE THERMODESORPTION METHOD

nA\mathop \rightleftharpoons \limits_K \left\{ {{A_n}} \right\}_{ads}^K \to \left\{ {{A_n} - mL} \right\}_{ads}^K + mL

Effect of the modification of diamond by methane on its oxidation in the presence of metallic catalysts

(1) where A represents a carbon-containing molecule, that is a polycondansation monomer; {A n } ads κ - a polymeric condensing product adsorbed on the catalyst; n — the degree of the molecular condensing; {A n - mL{ ads κ - remaining on the catalyst solid condensing products with C-C-bonds of one or other crystalline modification of carbon or of different polymeric forms of one; L - light molecules removing during the polycondensation process.