Journal of Crystal Growth, Vol.417, 31-36, 2015
SiGe crystal growth aboard the international space station
A silicon germanium mixed crystal Si1-xGex (x similar to 0.5) 10 mm in diameter and 9.2 mm in length was grown by the traveling liquidus-zone (TLZ) method in microgravity by suppressing convection in a melt. Ge concentration of 49.8 +/- 2.5 at% has been established for the whole of the grown crystal. Compared with the former space experiment, concentration variation in the axial direction increased from +/- 1.5 at% to +/- 2.5 at% although average Ge concentration reached to nearly 50 at%. Excellent radial Ge compositional uniformity 52 +/- 0.5 at% was established in the region of 7-9 mm growth length, where axial compositional uniformity was also excellent. The single crystalline region is about 5 mm in length. The interface shape change from convex to concave is implied from both experimental results and numerical analysis. The possible cause of increase in concentration variation and interface shape change and its relation to the Iwo-dimensional growth model are discussed. (C) 2014 Elsevier B.V. All rights reserved
Keywords:Diffusion;Convection;Growth from solution;Travelling solvent zone growth;Germanium silicon alloys