Growth Mechanisms in Germanium Dendrites: Three Twin Dendrites; Experiments on and Models for the Entire Interface

Abstract

The measured growth velocity of three twin germanium dendrites has been related to melt undercooling and to one of the twin spacings, and can be explained by the theory for two twin dendrites of this spacing. Three twin dendrites differed from two twin dendrites in that they grew at lower undercoolings, and, when propagation was possible, grew as fast or faster in the reverse or [2̄11] directions as in forward or [21̄1̄]'s. Irrespective of twin structure, the theory of Horvay and Cahn fitted parabolic decanted interfaces, provided the undercooling was taken to be that apparent at the tip and not that of the melt. Calculations from a model show layer nucleation to be possible on part of the interface and provide a rational for the understanding of H‐arm growth. The spacing of certain facets is found to agree moderately well with predictions of the theory of Mullins and Sekerka on morphological instabilities.