ON THE GROWTH OF (110) TWIN DENDRITES IN UNDERCOOLED GE

The microstructures of [110] twin dendrites were studied in detail. It was found that the periphery surfaces of the dendrite are all {111} p lanes. A [110] twin dendrite model was constructed to explain the grow th morphology. The model predicts the absence of branching except in t he initial stage, which has indeed been observed experimentally. From the model, it turns out that the [110] growth is in fact a combination of two [211] twin dendritic growths if the latter can maintain their coherency. Finally, the [110] to [211] dendritic transition is attribu ted to the break-up of the coherent growth of the two [211] dendritic growths.