First stages of diamond nucleation on iridium buffer layers

During the first stages of epitaxial diamond nucleation by the bias-enhanced nucleation procedure on monocrystalline iridium films the metal surface shows a characteristic roughening. Two different types of furrows and ridges along < 100 > and < 110 > develop. From atomic force microscopy images a typical structure height of 3 nm is deduced. Transmission electron microscopy indicates {111} faceting. In addition, after 45 min of nucleation 5-10 nm large structures are found with a typical distance of 100-300 nm showing a bright contrast in scanning electron micrographs. While a subsequent 30 min growth step results in a similar density of diamond grains with a size of approximately 100 nm, prolonging the biasing step does not increase the size of these nucleation centers. It is shown that under the present bias-enhanced nucleation conditions large diamond grains are etched. The fact that diamond can nucleate under conditions under which diamond cannot grow has strong implications on the nature of the observed nucleation centers and on theoretical models describing the nucleation process. (C) 2001 Elsevier Science B.V. All rights reserved.