Theoretical and Modeling Studies on Diamond Nucleation

Compared to the significant development in nucleation enhancement methods, fundamental scientific issues related to diamond nucleation processes remain less well addressed. In this chapter, the theoretical and modeling studies on surface nucleation of diamond are reviewed on the basis of available literature. 

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The theoretical model ing of the kinetic aspects of diamond nucleation processes is indeed scarce in published literature. Although attempts have been made to model the nucleation kinetics,as reviewed above, the approaches require an accurate estimation of the kinetic rate constants, necessitating fitting the kinetic model to experimental data, thereby making the model system- (or experiment-) dependent. In addition, the kinetics of surface diffusion of adatoms and the formation of intermediate carbonaceous phases were not considered in these studies. As indicated in Ref. 217, a kinetic model is expected to contribute to a better understanding of the role of SiC formation in the nucleation of diamond on a Si substrate. However, the kinetic scheme employed in these studies was, in fact, unable to distinguish between a Si and a SiC surface. To capture the possibil ity that an intermediate carbonaceous phase (such as DLC, carbide or graphite) may form prior to diamond nucleation, the kinetic model should be modified to includea time dependence of the density of nucleation sites determined by the kinetics of the formation of the intermediate phase. Further studies are therefore needed to construct a clear picture of the kinetics of diamond nucleation processes in CVD. 

Theoretical modeling of diamond nucleation kinetics is scarce in published literature. Some existing approaches require an accurate estimation of kinetic rate constants, which has been made on the basis of empirical and experimental data, and hence is system- (or experiment-) dependent. Therefore, further studies are still needed to improve the fundamental understanding of diamond nucleation kinetics. 

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