Abstract
Two kinds of experiments are carried out in Spacelab-J. In the first experiment, spherical single crystal of Si was used as a starting material and this crystal was melted and regrown in a furnace with almost uniform temperature distribution. In the second experiment, the starting material was Si rod of single crystal and the rod was heated in a temperature gradient to form a molten sphere at high temperature end of the rod. Then, the growth was started from melt-solid interface with un-melted rod as a seed cystal. It was found that there was a loss of Si from spherical melt in the first experiment due to the eutectic reaction between Si melt and Ta cartridge through a small hole in quartz crucible. The shape of the regrown crystal was hemi-spherical and on the surface of spherical part several facets were observed. The grown crystal was cut and mechanically polished. The chemical etching showed the presence of strong impurity striation in the part grown on the ground while no striation was observed in the space grown part. This means that unsteady Marangoni flow was successfully suppressed as well as thermal convection because of a uniform temperature distribution in the growth cell. In the melting process of Si rod, the molten sphere with 19 mm diameter was formed at one end. However, this molten sphere had moved from the tip to the side of the rod and the sphere touched with quartz tube. Due to this event, the crystal was broken. It turned out that the growth was done from un-melted rod but the growth direction was perpendicular to its axis.
