Growth of Hg2Cl2 and Hg2Br2 single crystals by physical vapor transport

Large crystals of Hg2Cl2 and Hg2Br2 (48 mm in diameter, up to 600 g in weight) have been grown by the physical vapor transport (PVT) technique in closed ampoules in vertical configuration without contact with the ampoule walls. The starting materials have been pre-purified by resublimation. Seed selection has been accomplished by having a narrow tubing at the tip of the growth ampoule. Thermochemical analysis of the system is done and discussed. The grown crystals show good transparency and good crystallographic quality. An acousto-optic modulator built from the Hg2Cl2 crystal showed good performance consistent with predicted device parameters.