Solidification behavior of falling germanium droplets produced by pulsated orifice ejection method

In order to clarify containerless solidification mechanism of falling semiconductor microdroplets, the monosized droplets of germanium in the size range from 200 to 500 μm were ejected by pulsated orifice ejection apparatus method. The density of grains in the resultant particles was dramatically reduced by decreasing the ejection temperature, i.e. initial temperature. A surface observation and orientation imaging microscopy analysis proposed that such microstructural transition was derived from the dependency of preferred growth direction on the undercooling level: the initial temperature determined the solidification undercooling. Numerical calculation with the classical nucleation theory was performed to discuss this phenomenon, but could not sufficiently elucidate the effect of initial temperature obtained experimentally.