DIAMOND NUCLEATION BY HYDROGENATION OF THE EDGES OF GRAPHITIC PRECURSORS

How diamond films grow by chemical vapour deposition is now fairly wel l understood1,2, but the mechanism by which the diamond phase first nu cleates is still unclear. Evidence is accumulating that atomic hydroge n, known to be important in diamond growth1,2, also plays an important role in nucleation3,4. The nature of the carbon precursor to diamond has been much debated2-9; although there is some evidence that graphit e is formed before diamond nucleation2,5,6 and that diamond grows epit axially on the graphite edges7, others have suggested10,11 that graphi te formation is detrimental to diamond nucleation. Here we present cal culations that suggest that diamond films can nucleate by the initial condensation of graphite and subsequent hydrogenation of the {1100BAR} prism planes along the edges of the graphite particles. If nucleation really does occur in this manner, the understanding that our model pr ovides should assist in the development of methods for growing large d iamond single crystals (now limited in part by secondary nucleation of independent crystals) and highly oriented epitaxial diamond films.