Microstructures of undercooled germanium droplets

Undercoolings at crystal nucleation onset of liquid Ge droplets are measured and the microstructures of the droplets are examined. Undercooling values ranging from 150-415 + or 20 C were obtained. It is observed that for the samples undercooled less than 300 C prior to solidification the grain size was greater than 100 microns; for samples undercooled between 300-400 C the grain size was between 50-100 microns; and for samples undercooled greater than 400 C the grain size was 10-20 microns. Consideration is given to dendritic growth and interfacial undercooling. It is noted that there is a correlation between undercooling and as-crystallized grain structure.