The characterization of dislocations structure in large-sized sapphire single crystal by SAPMAC method

【作者】 汪桂根； 张明福； 左洪波； 赫晓东； 韩杰才； 姚泰；

【Author】 WANG Gui-GenZHANG Ming-FuZUO Hong-Bo) HE Xiao-Dong) HAN Jie-CaiYAO Tai(Center for Composite Materials, Harbin Institute of Technology,Harbin 150080, China P.R.

【机构】 Center for Composite Materials, Harbin Institute of Technology, Harbin 150080, China P.R.；

【Abstract】 Combined with remarkable mechanical and physicochemical properties, the sapphire (Al2O3) single crystal has wide applications in modern Hi-Tech fields, from military and commercial optical systems to high power laser components and semiconductor substrates. The large-sized (?225×205mm, 27.5kg) a-plane (11-20) sapphire single crystal was grown by SAPMAC method (sapphire growth technique with micro-pulling and shoulder at cooled center). However, dislocations are the most frequent and important extended defects in sapphire crystal, which have significance for the growth, property and the plastic deformation of sapphire crystal. Thus the dislocations distribution, dislocations density and Burgers vector of selected dislocations in the sapphire boule from different crystal regions were studied by chemical etching, scanning electron microscope and Laue X-ray transmission topography. The experimental results show that the dislocations density is about 8.5×102-4.6×103/cm2, and is decreasing gradually from the crystal top region to the bottom portion. The clear and stable contrast images of hexagonal, triangular and quadrilateral etch pits were observed in different crystal planes (C (0001), M (10-10), A (11-20)), which demonstrates the crystal structure symmetry. The analysis of Burger vector of dislocations lay C (0001) basal plane confirms pure edge type having (11-20) and (10-10) type Burgers vector. Finally, the origins of crystal dislocations are discussed, and it is suggested that the sapphire crystal grown by SAPMAC method has relatively low dislocations density and high crystal quality because of its low temperature gradient and low crystal growth velocity.更多还原