X-RAY TOPOGRAPHY CHARACTERIZATION OF Ge(Ga) SINGLE CRYSTALS GROWN BY THE FLOATING ZONE METHOD IN MICROGRAVITY

摘要

Results of practical application of X-ray diffraction methods for study of structural peculiarities of crystals caused by special features of solidification process in microgravity are given in this work. The crystal under investigation was obtained by FZ remelting in space conditions of <111> single crystal Ge rod (15 mm in diameter and 135 mm in length) grown by Czochralski method and doped with ～10~(18) cm~(-3) Ga. Real structure of the crystal obtained was analyzed by X-ray topography and double crystal diffractometry methods together with metallography and spreading resistance measurements. Both reflection and transmission topographs were recorded from the individual specimens to visualize the defect microstructure developed in the crystal during its growth. It was established that the structure of the crystal is characterized by the presence of an imperfectly melted region (20 mm in length) and defects associated with it. Anomalous transmission topography reveals the cellular structure of dislocations in the core of the crystal with an average density of about 4·10~3 cm~(-2). Striations that were clearly revealed in the whole crystal by metallography method suggest that unsteady Marangoni convection was induced during floating zone growth under microgravity conditions.