Comparative Analysis of Hg2Br2 and Hg2BrxCl2-x Crystals Grown via PVT

In this study, we comparatively analyzed the physical properties of Hg2Br2 and Hg2BrxCl2−x crystals synthesized via physical vapor transport (PVT). Prior to crystal growth, the elemental mapping images obtained through scanning electron microscopy/energy-dispersive spectroscopy clearly showed the presence of Cl atoms (2.62%) in Hg2BrxCl2−x powder; however, Cl atoms were not detected in Hg2Br2 powder. After crystal growth by PVT, each single crystal was characterized using various analysis techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. It was observed that the introduction of Cl elements into Hg2Br2 crystals strongly affected the crystallinity and Raman vibration modes. Hence, this in-depth material characterization study proposed a feasible method to screen impurities in mercury halide crystals

In-depth Investigation of Hg2Br2 Crystal Growth and Evolution

Physical vapor transport (PVT) has frequently been adopted for the synthesis of mercurous bromide (Hg2Br2) single crystals for acousto-optic modulators. However, thus far, very few in-depth studies have been conducted that elucidate the growth process of the Hg2Br2 single crystal. This paper reports an in-depth investigation regarding the crystal growth and evolution behavior of the Hg2Br2 crystal with facet growth mode. Based on the experimental and simulation results, the temperature profile conditions concerning the seed generation and seed growth could be optimized. Next, the PVT-grown Hg2Br2 crystals (divided into single crystal and quasi-single crystal regions) were characterized using various analysis techniques. The single-crystal Hg2Br2 was found to possess a more uniform strain than that of the quasi-single crystal through a comparison of the X-ray diffraction data. Meanwhile, the binding energy states and electron backscatter diffraction images of the as-synthesized Hg2Br2 crystals were similar, regardless of the crystal type. Furthermore, Raman spectroscopy and transmission electron microscopy analyses provided information on the atomic vibration mode and atomic structures of the two kinds of samples. The synergistic combination of the simulation and experimental results used to verify the growth mechanism facilitates the synthesis of high-quality Hg2Br2 crystals for potential acousto-optic tunable filter device applications