A heat shield to control thermal gradients, melt convection, and interfaceshape during shouldering in Czochralski oxide growth

A modification of the Czochralski growth system consisting of a circular di sk attached to the pulling rod has been used during the shouldering of Bi12 SiO20 Single crystals. Experimental results show significant changes to the melt-crystal interface shape and faceting behavior from the use of disks o f different materials. A simple mathematical analysis of enclosure radiatio n provides a self-consistent explanation for the observed changes in terms of system thermal gradients and the intensity of melt convection. (C) 1999 Elsevier Science B.V. All rights reserved.