Growth of Bi and Bi1−xSbx single crystals with specific properties

Abstract

We grew single crystals of Bi and Bi_1−xSb_x by the Czochralski technique and studied the influence of the axial temperature gradient in the crystal, the angle β between the (111) plane and the growth direction, growth rate f, rotation rate of the crystal and crucible, and alloy composition. A low temperature gradient transformed the smooth surface parallel to the (111) plane into a corrugated surface in the pulled single crystal. A high temperature gradient formed internal stress and cracks in the crystal. These cracks in the Bi_0.91Sb_0.09 single crystal increased the resistivity through the increase of surface voltage drop at 90–300 K temperature due to bulk Dirac electrons, as a result of bilayer exfoliation. The Bi single crystal with 15 mm diameter was grown in the (111) direction with a temperature gradient of G_c = 10 K cm⁻¹ using the developed growth conditions. The increase of the temperature gradient transformed the pulled Bi single crystal in the (111) direction into a polycrystal. Bi_1−xSb_x single crystals were grown with diameters up to 20 mm using a solid Sb feed. With the addition of Sb, we increased the temperature gradient up to G_c = 50–65 K cm⁻¹, the angle β up to 5–20°, and reduced the growth rate f down to (25–1.67) × 10⁷ m s⁻¹. The calculation of constitutional supercooling and morphological stability criterion confirmed the chosen growth parameters for Bi_1−xSb_x alloys. The developed technique for the growth of Bi and Bi_1−xSb_x single crystals can be used to study their properties and for practical applications.