The evolution of growth modes and activity of growth sources on canavalin investigated by in situ atomic force microscopy

In situ atomic force microscopy has been used to investigate the evolution of growth modes and the activity of dislocation sources as a function of supersaturation during canavalin crystal growth. The results presented here show that, depending on the supersaturation, growth occurs on monomolecular steps generated either by simple or complex screw dislocation sources, 2D nucleating islands, or macroclusters that sediment onto the surface before spreading laterally as step bunches. We have observed the process of an individual dislocation source generating new steps which can be used to directly measure the critical length necessary for steps to advance. The activity of various dislocation sources are investigated as a function of supersaturation. A comparison of fundamental materials parameters for canavalin and a variety of other systems show systematic scaling. The kinetic coefficient decreases as the molecular complexity increases and the supersaturation at which 2D nucleation is observed increases with step free energy. (C) 2000 Elsevier Science B.V. All rights reserved.