Study of crystal-crucible detachment: GaSb in SiO2

Abstract

The mechanism of crystal–crucible attachment, followed by detachment, is studied in the case of the Bridgman growth of GaSb in a SiO₂ crucible. Experiments show that this mechanism is periodical and occurs all through the solidification. It is postulated that the attachment is due to the GaSb–SiO₂ energy of adhesion and that detachment occurs when the thermo-elastic energy, due to crystal-crucible differential dilatation, exceeds the adhesion energy. A numerical model is developed with Comsol®, based on this hypothesis, which takes into account the thermal field in the sample and the thermo-elastic stresses. Comparison of the elastic energy with the adhesion energy shows a good agreement with the experimental results, in terms of the temperature at which detachment occurs, provided that the stress is limited by the critical resolved shear stress. A qualitative agreement is also found between the calculated plastic relaxation and radial distribution of dislocations in the crystal.