In-situ observation of instability of a crystal-melt interface during the directional growth of pure antimony

The instability of a crystal-melt interface during the directional growth of pure antimony was studied using an in-situ observation technique. The morphology of the crystal-melt interface was planar at a low growth velocity, while the interface transitioned to wavy and then zig-zag faceted at 60 μm s^-1. Calculating the thermal field at the crystal-melt interface using a diffusion equation showed that the temperature gradient in the melt becomes negative when the moving velocity of the interface is higher than 52 μm s^-1. These results demonstrate that perturbations introduced into the planar interface are amplified by a negative temperature gradient and these amplified perturbations result in zig-zag facets.