Influence of thermal phenomena on crystal reattachment during dewetted Bridgman growth

A finite-element model that accounts for details of the melt meniscus, the solid-liquid interface, and heat transfer is applied to a model system representing dewetted Bridgman growth. A new mechanism involving the thermal field and the meniscus position is proposed to explain crystal reattachment during dewetted Bridgman growth method. Crystal reattachment after an initial dewetted growth is posited to proceed via a melt cooling phenomenon that occurs when the melting-point isotherm advances above the melt meniscus position. Conditions to maintain detached growth are achieved when the solidification isotherm falls below the meniscus during the whole growth process. Model results show that these conditions are difficult to meet under typical melt-ampoule wetting angles and gas pressures in a simple, constant-gradient furnace. More promising conditions to promote and maintain dewetted growth are predicted for multi-zone furnace profiles. The results are consistent with prior experiments and point to the importance of optimizing the thermal conditions for successful dewetted growth.