Crystal Perfection Affected by Seed Orientation with Different Supercooling. A Qualitative Model

AbstractAn attempt is made to prove that the growing of semiconductor crystals of diamond of or ZnS structure in 〈111〉 direction on a seed in a melt is not always advisable under actual conditions of growth, meaning the crystal perfection. Two factors are shown to be responsible for crystal perfection, the face perfection in an equilibrium state and the perfection occurring in the growing process, due to a meltcrystal system deviation from the equilibrium state. The first one is a function of free surface energy of the face, Es, while the second one is a \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{d\Delta F}}{{dt}}} \right)_v $\end{document} function, i. e. depending on a difference in phases free energies variation rate.Relationship of crystal perfection, S, and growing conditions may be conceived generally as \documentclass{article}\pagestyle{empty}\begin{document}$ S_{(hkl)} = \psi \,\{ E_{s(hkl)} \} \, + \,\varphi \,\left({\frac{{d\Delta F}}{{dt}}} \right)_\upsilon $\end{document}. The first term of the equation practically is not changing at different supercoolings, the second is subjected to considerable variations. In 〈111〉 direction grown crystals will be the most perfect at lower supercooling. With higher supercooling the best perfection will be obtained in another than 〈111〉 direction.