To investigate interface shape and thermal stress during sapphire single crystal growth by the Cz method

Global modeling is performed to predict electromagnetic field, heat transfer, melt flow, solid/liquid (S/L) interface shape, and thermal stress during RF-heated Czochralski (Cz) single crystal growth of sapphire. The relations between the convexity of the S/L interface and growth parameters, i.e., crystal rotation rate, crystal size, furnace insulation, and RF coil, are established. Thermal stress is represented by the von Mises stress, and the stress status in the growing crystal is characterized by the maximum von Mises stress. The curves regarding growth parameters and the maximum von Mises stress are obtained. According to the analysis, a flat or slightly convex S/L interface could be achieved by modifying the growth parameters, and the crystal quality could be improved by reducing thermal stress and its related defects. (C) 2012 Elsevier B.V. All right sreserved.