Defect-induced stabilization of diamond films

Abstract

THE growth of diamond thin films by low-pressure vapour deposi-tion should find technological applications in such diverse fields as hard coatings for cutting tools, lens coatings, heat sinks and electronics1–4. Under such growth conditions diamond should be unstable relative to graphite, yet diamond is formed in practice. Present approaches to describing the growth of diamond explain this paradox by means of a variety of surface kinetic reactions that are controlled by concentrations of adsorbed hydrogen and hydrocarbon radicals5–8. Here we propose a simpler explanation, that high vacancy concentrations are present near the growth face of the diamond film. The formation energy of vacancies in diamond is lower than in graphite, so that large vacancy concentrations (1–8%) can raise the formation energy of graphite above diamond, permitting nucleation and stable growth of diamond. This quasi-thermodynamic model is fundamentally different from the kinetic models for diamond film growth, and predicts that the growth of films with low defect concentrations will be difficult.