Heat transfer and interface inversion during the Czochralski growth of yttrium aluminum garnet and gadolinium gallium garnet

Computer-aided simulations are performed using an integrated process model for the Czochralski (CZ) growth of yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG). Internal radiant heat trabsfer through the crystal is responsible for the deeply convex melt/crystal interface and the propensity for crystal cracking with large cone angles during CZ YAG growth. The nature of interface inversion by crystal rotation is fundamentally different for YAG growth under low and high thermal gradients. Results suggest that classical "flat-interface" growth via crystal rotation is attainable for YAG growth only under low-gradient thermal conditions, while this limitation is not as stringent for the growth of GGG. The depth of the melt is also shown to affect interface inversion for GGG. The complicated dependence of interface inversion on many system details, rather than solely crystal rotation, suggests that this effect is not adequately described by simple, universal scalings which have been previously proposed.