Block Formation and Crystallographic Orientation Changes During Growth of Shaped Sapphire Single Crystals

The crystallographic orientation of shaped crystals grown by the Stepanov method is determined by the seed orientation. The original orientation persists if the crystal grows ideally enough. However, crystals often contain structural defects such as dislocations and their pileups, slip bands, and intergrain boundaries. Each of these defects is connected with a certain distortion of the crystal lattice. As a result, the orientation of the grown crystal differs from the initial one and varies throughout the volume. The orientation changes little during growth if the crystal contains few defects. The crystal orientation can change quite significantly if the defect density is high. Until now, studies of the change of crystal orientation during pulling have been limited to an examination of twinning effects.