TWINNING AND FACETING IN EARLY STAGES OF DIAMOND GROWTH BY CHEMICAL VAPOR-DEPOSITION

Flat, hexagonally shaped diamond platelets were observed during the initial stage of microwave plasma assisted deposition of diamond. The platelets are approximately 2.5 Am in linear dimension and are oriented with their large six-sided faces parallel to the silicon substrate. A re-entrant groove, running parallel to the large six-sided face, is present in the small side faces of the platelets. Larger diamond crystals, with a fully developed three-dimensional morphology, all have re-entrant grooves in other directions. The observations support the hypothesis that the growth rate of {111} faceted diamond crystals is greatly enhanced by the presence of microtwins (multiple stacking errors), which give rise to re-entrant comers where they intersect the crystal surface. Fully developed {111} faceting and a strong influence of re-entrant comers is expected when the average lifetime of a carbon atom bonded once to the surface is much less than the average time between addition of adatoms at adjacent surface sites.