Study of the effect of crystallization parameters on gaseous inclusions in sapphire ribbons grown by the Stepanov method

The effect of growth parameters on the two main types of gaseous inclusions in sapphire ribbons-bubbles in the crystal bulk and near-surface pores-have been investigated. The parameters, providing a minimum number of bubbles and a minimum thickness of the surface porous layer, are determined. The experimental data are obtained during the commercial production of sapphire single crystals by the Stepanov method using an expert software package that provides automatic collection and treatment of the process data and the results of a crystal-quality analysis. The effect of the following parameters is considered: the derivative of the mass sensor signal, which indirectly characterizes the temperature of the shaping surface and the melt meniscus height; the seeding power; the melt exposure time in a crucible before seeding; and the technique of shaper preparation.