SOLIDIFICATION OF HIGHLY UNDERCOOLED SI AND GE DROPLETS

The production of small (5-200 nm) spheres of silicon and germanium from their melts by electrohydrodynamic atomisation (EHD) was previously reported [1]. We have examined the formation of amorphous and crystalline phases in such spheres. Analysis of electron diffraction data reveals that the smallest spheres are amorphous, with a tetrahedrally coordinated covalent random network structure, rather than being either very fine grained polycrystals or configurationally frozen metallic liquids. The formation of the semiconducting amorphous and crystalline phases is considered in terms of a competitive classical nucleation analysis, and good agreement is found for the relative proportion of each phase as a function of sphere size. © 1990.