Step structures on the {00•1} facets of single crystals which had been grown using the modified Lely method were examined by means of optical and atomic force microscopy. The results were compared with those obtained using the chemical vapor deposition method. The step structures around micro-pipes were quite different for differing polarities of the growing surface. Step bunching was more favored on Si faces than on C faces. A single large step with a height of 8c, and 18 steps with a height of c/2, were typically observed to propagate from micro-pipes at the center of each spiral on the Si-faces and C-faces, respectively, of 6H-type crystals. No micro-pipes were detected at the center of spirals with a step height of 1.5nm in 6H-type material. The motion of dislocations was monitored by successively etching and polishing a grown crystal from the surface to the inside. It was noted that the screw dislocations shifted outwards, by 10 to 40μ, from the center of a giant spiral during 200μ of vertical growth. On the other hand, edge dislocations could glide in any direction.

N.Sugiyama, A.Okamoto, K.Okumura, T.Tani, N.Kamiya: Journal of Crystal Growth, 1998, 191, 84-91