KINETICS OF THE INITIAL-STAGES OF CVD DIAMOND GROWTH ON NON-DIAMOND SUBSTRATES - SURFACE CATALYTIC EFFECTS AND HOMOEPITAXY

Recently, we have reported that the density of chemical vapour deposit ion (CVD) diamond particles obtained on non-diamond substrates abraded with a diamond slurry can be enhanced by a few orders of magnitude by abrasion with a mixed metal/diamond slurry. In this work, we present growth kinetics studies of isolated diamond crystallites (prior to coa lescence into a continuous film), which are formed at the initial stag es of deposition on metal/diamond and diamond-pretreated silicon. The metals used were Ti, Fe and Cu. It has been found that the temperature dependence of the diamond growth rates on differently pretreated subs trates can be described by an Arrhenius plot. From these plots, it has been concluded that at the initial stages of deposition the activatio n energy for CVD diamond formation, as observed for diamond-abraded su bstrates, can be substantially decreased as a result of substrate surf ace pretreatment with a mixed metal/diamond slurry. However, after coa lescence of the crystallites into a continuous film, the activation en ergies for metal/diamond and diamond-pretreated substrates were found to be similar. Based on micro-Raman measurements it has been found tha t at the initial stages of deposition, the quality of diamond that was grown on the metal/diamond abraded substrates is higher than that dep osited on the diamond-abraded ones. In contrast, after a long depositi on time, the quality of diamond grown on the differently pretreated su bstrates was found to be similar. It is suggested that the observed ef fects are associated with the metal's catalytic activity towards the h ydrogenation of unsaturated hydrocarbons, namely enhancing the concent ration of sp(3)-bonded hydrocarbon fragments. At the initial stage of deposition, before a stable substrate is formed, this enhancement lead s to an increase in the diamond growth rate, lowering of the activatio n energy for its homoepitaxial growth on diamond residues left by pret reatment, and improvement of its quality. (C) 1997 Elsevier Science S. A.