GROWTH STUDY OF LARGE NON-SEEDED PB1-XSNXTE SINGLE-CRYSTALS

Large single crystals of Pb1-xSnxTe (x∼0.20) were grown by sublimation on the quartz surface of a closed ampoule. Initial undercritical supercooling provided nearly equilibrium conditions for in situ nucleation of a monocrystalline seed from which a high quality single crystal could be grown at a high growth rate. The presence of free elements in untreated charges had a strong influence on the concentration of imperfections, i.e. inclusions, holes, dislocations and low angle grain boundaries. Excess Te (δ∼ 0.01 mole %) in the annealed charge was necessary for the nucleation of a solid monocrystallite through a vapor-solid mechanism, leading, under appropriate thermal conditions, to the growt of a high quality single crystal. The apparent growth rate of the as-grown crystals appeared to be linearly dependent on the undercooling δT in the entire range (0≤δT≤25‡C) studied and it was found to be greatly influenced by deviation of the charge from stoichiometry. No apparent effect of the growth orientation on the overall growth rate was found. The crystal habit and possible driving forces of the crystal growth are qualitatively discussed. © 1979 AIME.