STEP BUNCHING ON VICINAL STEPPED FACES GROWING FROM SOLUTIONS AND MELTS. A. A. Chernov, S. R. Coriell, B. T. Murray, G. B. McFadden, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

We try to answer the questions: Why and when does the equidistant train of elementary steps on a growing vicinal face reorganize itself into step bunches? These bunches are responsible for various crystal defects. The anisotropic interface kinetics, solution or melt flow, growth steps motion and capillarity are taken into account. Random perturbation of the growing vicinal face was analyzed in order to find out the range of the "resonance" wave-lengths that cause step bunching, i.e., morphological instability. Detailed theory and some experiments show that liquid flow directed opposite to step flow results in stabilization while parallel flows cause step bunching. The tangential solution flow should influence the morphological stability of a growing interface if the rate of this flow at a distance of the order of the perturbation wavelength from the surface is comparable to the rate at which the step perturbations move. It was found that there are conditions of self-stabilization by the step flow only and conditions of absolute stability in the presence of liquid flow.

Universities Space Research Association, 4950 Corporate Drive, Suite 100, Huntsville, AL 35806 and on leave from the Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Leninsky Prosp 59, Russia