Growth Mechanisms of Germanium Dendrites: Kinetics and the Nonisothermal Interface

Abstract

The growth of germanium dendrites containing two twin planes has been investigated. The solution of the heat flow problem in the stem of a growing dendrite being pulled from a melt permitted the design of experiments suitable for testing theory. The limiting growth velocity was determined as a function of melt undercooling for a number of twin spacings. Tip radii were measured on decanted interfaces, many of which were found to have parabolic sections. The data for these could be fitted with the theory for dendritic growth assuming a layer flow mechanism with a rate constant ≥3 cm/sec‐°C. The only adjustable parameter is the average interfacial energy which may be as little as 15% less than the expected value, although lower values result in a somewhat more satisfactory fit. All the dendrites observed appear to grow under the condition that the magnitude of the tip radii is determined by the presence and spacing of the twins, and not under the condition of maximum velocity.