Abstract
Sapphire single crystal is widely used in a variety of modern applications from GaN-based LED to military optical systems because of its excellent combination of optical, mechanical, thermal and chemical properties. The dislocations affecting the quality of sapphire crystal were studied by chemical etching and optical microscopy in this paper. The experimental results showed that the dislocation corrosion pits of (11-20) plane in sapphire crystals grown by Kyropoulos method is diamond-shaped and (1-102) plane is isosceles triangle and the density of dislocations in samples grown by Czochralski method is about two orders of magnitude higher than that in samples grown by Vertical Bridgman method. The formation mechanism of defects and proposes was also discussed.