Rapid solidification into undercooled melt of ge by means of levitation technique

Using CO₂ laser equipped electro-magnetic levitator, we carried out the containerless crystallization of Ge. From the point of the interface morphologies, the relationship between growth velocities and undercoolings was classified into two regions, I and II. In region I where the plate-like needle crystals were observed, the growth velocities are expressed by two dimensional (2D) nucleation-controlled growth model. In region II, where the morphology of growing crystals changed to massive dendrites, the growth velocities are approximately expressed by linear kinetics growth model. These results indicate that with increase of undercooling, the rate-determining factor changes from 2D nucleation on the faceted interface at the reentrant corer, which was formed at the edge of the multiple twin boundaries, to random attachment of atoms on the nonfaceted interface.