Study of crystal-crucible detachment: GaSb in SiO2

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.