Growth kinetics of faceted solid-liquid interfaces and kinetic roughening

Abstract

We have recently carried out a detailed investigation of interfacial kinetics of Ga growing into supercooled melt. The dislocation-assisted and dislocation-free growth rates were measured in the range of 10 −3 to 2×10 4 μm/s and interfacial supercoolings in the range 0.01 to 4.5°C for the [111] and [001] crystal orientations. The experiments show that the faceted interfaces become nonfaceted, “kinetically rough”, as the interface supercooling increases. The faceted-nonfaceted transition temperature depends on the orientation and perfection of the interface with respect to dislocation(s). The results are compared to those predicted from the existing theoretical rate equations which show qualitative agreement but not quantitative. In order to obtain quantitative agreement between the two, the liquid next to the interface should be considered as “diffuse” so that its average properties gradually attain those of the bulk; in this region the interfacial diffusivity is much smaller than the liquid self-diffusion coefficient. Moreover, the step free energy, which becomes negligible as the interface becomes kinetically rough, should be taken as a function of the interface supercooling.