Monocrystalline samples of -phase material were studied by means of X-ray topography. The samples were grown in the [00•¯1] or [1¯1•0] directions by using a modified Lely method. Wafers which were perpendicular or parallel to the growth direction were sliced from the crystals and were examined by making transmission topographs via the Lang method. It was found that the 2 types of crystal exhibited marked differences with respect to the types and densities of defects which were present. Both crystals contained a number of structural defects which extended along the growth direction. Micro-pipes and screw dislocations were observed in the [00•¯1] crystals, while stacking faults and edge dislocations were found in the [1¯1•0] crystals. In addition, the [00•¯1] crystals contained misoriented sub-grains with tilt and twist components, whereas the [1¯1•0] crystals contained only tilted sub-grain boundaries. It was concluded that most of the defects were generated during the very first stages of growth.

J.Takahashi, N.Ohtani, M.Kanaya: Journal of Crystal Growth, 1996, 167, 596-606