Physical Vapor Transport Process for Highly Purified Hg2Br2 Crystal: from Powder Purification to Crystal Growth

Abstract

High quality Hg2Br2 crystal grown <i>via</i> the physical vapor transport (PVT) process is essential for the fabrication of the acousto-optic tunable filters (AOTFs) module. The full process flow, including powder purification and crystal growth, should be systematically established, but there have been few reports about the fully established process flow of single Hg2Br2 crystal. In this study, we report on the entire process, from purification of the Hg2Br2 powder to crystal growth based on the PVT process. We compared the raw powder and purified powder using X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). Although there was no considerable difference in the XRD and XPS results of the powders before/after purification, the ICP impurity analysis indicated that the purity of Hg2Br2 powder increased from 4N (99.99%) to 5N (99.999%). The Hg2Br2 single crystal grown by the PVT process was then fully characterized by XRD, XPS, and Raman spectroscopy. The vibration bonds constituting the Hg2Br2 lattice were clearly identified from the Raman spectra of the final Hg2Br2 crystal. High quality Hg2Br2 single crystal PVT-grown from the purified powder will lead to the development of a high-performance acousto-optic module. Establishing the systematic growth sequence of the Hg2Br2 based on PVT paves the way to promising AOTF modules.