8 - Theoretical and Modeling Studies on Diamond Nucleation

Abstract

This chapter focuses on the theoretical and modeling studies on diamond nucleation. In thermodynamic theory of heterogeneous nucleation of solid from vapor, a nucleus on a substrate is considered to be cap-shaped with a contact angle to the substrate. Diamond is a metastable phase under chemical vapor deposition (CVD) conditions. The processes competing with diamond nucleation and growth are the nucleation and growth of graphite or amorphous carbon, as well as spontaneous graphitization of the diamond surface. The graphite nuclei may also contribute to creation of planar defects, which along with other defects, constitute the major obstacles to growth of single crystal diamond. The free-energy differences between these carbon phases are relatively small. The presence of a diamond surface, for example, an epitaxial or diamond-seeded surface increases the probability of diamond nucleation. There should be a small range of conditions under which the nucleation rate of diamond is greater than that of graphite.