卤化亚汞晶体及其在红外偏光/声光与核辐射探测器件中的应用

doi:10.16553/j.cnki.issn1000-985x.2025.0235

摘要/Abstract

摘要： Hg₂X₂ （X=Cl、Br、I）系列晶体具有红外透光范围宽、双折射大、声光品质因子大、声速和声衰减系数低等特点，是一类性能优良的中长波红外偏光与声光晶体材料，广泛应用于研制格兰·泰勒棱镜、渥拉斯顿棱镜等偏光器件及声光调制器、声光可调滤波器等声光器件，这些器件是高性能红外光谱仪、红外激光器、红外探测器的核心元件。此外，此类晶体的平均原子序数大、密度高、电阻率高、迁移率寿命积大，且兼具优异的半导体性能和近红外闪烁发光性能，在核辐射探测领域展现出巨大的应用潜力。本文系统综述了Hg₂X₂系列晶体的结构特征与物理性质，讨论了大尺寸晶体的生长方法，并深入分析了其在偏光器件、声光器件及辐射探测领域的应用进展，指出后续研究重点应聚焦于优化物理气相传输法工艺参数，提升晶体性能一致性，同时补充极端环境可靠性数据，推动其在更多实际场景中应用。

关键词: Hg₂X₂; 晶体生长; 物理气相传输法; 声光器件; 偏光器件; 核辐射探测

Abstract: The detection of electromagnetic waves—including infrared rays， visible light， ultraviolet rays， X-rays， gamma rays—is one of the most essential approaches for humankind to understand the world. In the ultraviolet-visible light band， detection technologies are relatively mature due to the well-developed materials such as crystalline silicon. However， numerous challenges still persist in the detection of extremely short-wave X-rays and gamma rays as well as long-wave infrared rays. In the field of infrared detection， HgCdTe （MCT） focal plane array detectors are capable of capturing thermal imaging that is invisible to the naked eye. Nevertheless， they are unable to provide spectral information due to the lack of infrared spectroscopic devices at the front end. Therefore， developing optical crystals for infrared polarizing prisms and infrared tunable filter devices forms the foundation for advancing infrared multispectral and hyperspectral detection. In addition， for the detection of highly penetrating X-rays and gamma rays， semiconductor-based detection and scintillator-based detection are the most extensively studied approaches. However， the commercial semiconductors CdTe and CdZnTe （CZT） suffer from non-uniform defect distribution and high production costs， while traditional halide and oxide scintillators are hygroscopic， costly， or have insufficient energy resolution. Hg₂X₂ （X=Cl， Br， I） crystals have emerged as a promising multifunctional alternative， combining exceptional infrared polarizing optical properties， strong acousto-optic performance， and high-performance radiation detection capabilities. Hg₂X₂ crystals crystallize in the I4/mmm space group， featuring one-dimensional X-Hg-Hg-X chains stabilized by intra-chain covalent bonding and inter-chain van der Waals interactions. Halogen substitution from Cl to Br and I enables systematic tuning of key material parameters： lattice constants increase， band gaps decrease （from 2.9 to 2.1 eV）， infrared transparency extends up to 40 μm （in Hg₂I₂）， and both birefringence and the acousto-optic figure of merit improve significantly （2 600×1.5×10^-18 and 3 200×1.5×10^-18 s³/g for Hg₂Br₂ and Hg₂I₂， respectively）. Notably， researchers at Shandong University have successfully grown high-quality and large-sized Hg₂Cl₂ and Hg₂Br₂ crystals with diameters up to 54 mm via physical vapor transport （PVT） method by optimizing temperature gradient， growth rate， and cooling profile to suppress defects such as impurities and cloud-like inclusions. Hg₂Cl₂ crystals have been employed for fabricating various polarizing devices such as Glan-Taylor prisms and Wollaston prism， which are operable within the spectral range of 3 μm to 20 μm. They exhibit an extinction ratio of 30 000∶1 and a laser-induced damage threshold （LIDT） of 8.06 J/cm² at 3.5 μm. Moreover， the anti-reflection-coated polarization beam combiner （PBC） achieves combination efficiencies of 93.5% at 4.6 μm and 92.4% at 9.2 μm， with excellent beam quality （M²=1.23/1.17）. For acousto-optic applications， Hg₂Br₂-based acousto-optic tunable filter （AOTF） represents the only viable solution for MWIR/LWIR operation， demonstrating internal diffraction angles greater than 7° and a peak diffraction efficiency of 97.35%， achieved through engineered acoustic absorption layers. In radiation detection， Hg₂X₂-based detectors achieve an energy resolution of 1.35% for 662 keV γ-rays from ¹³⁷Cs. Furthermore， Hg₂Br₂ enables dual-mode detection of γ-rays and thermal neutrons due to the high neutron capture cross-section of ¹⁹⁹Hg， and has been applied in wearable α-particle detectors for real-time monitoring of water contamination. This review highlights the pivotal role of Hg₂X₂ crystals in the fields of infrared and nuclear radiation detection， and offers perspectives on the challenges associated with their crystal growth and device fabrication.

Key words: Hg₂X₂; crystal growth; physical vapor transport method; acousto-optic device; polarization device; nuclear radiation detection

中图分类号:

宋剑, 岳中杰, 乔晓杰, 翟仲军, 张国栋, 陶绪堂. 卤化亚汞晶体及其在红外偏光/声光与核辐射探测器件中的应用[J]. 人工晶体学报, 2026, 55(3): 331-339.

SONG Jian, YUE Zhongjie, QIAO Xiaojie, ZHAI Zhongjun, ZHANG Guodong, TAO Xutang. Mercurous Halide Crystals and Their Applications as Infrared Polarization/Acousto-Optic and Nuclear Radiation Detectors[J]. Journal of Synthetic Crystals, 2026, 55(3): 331-339.

图/表 7

图1 Hg2X2系列晶体的结构与物理性质［27］。（a）晶体结构；（b）相变温度区间；（c）不同晶体的双折射与晶体透光范围的关系；（d）不同声光晶体的声光品质因子与透过范围的关系

Fig.1 Structure and physical properties of Hg2X2 crystals［27］. （a） Crystal structure；（b） phase transition temperature range；（c） relationship between birefringence and transparent range of different crystals；（d） relationship between acousto-optic quality factor and transparent range of different acousto-optic crystals

表1 Hg2X2系列晶体的物理性质

Table 1 Physical properties of Hg2X2 crystals

Property	Hg₂Cl₂	Hg₂Br₂	Hg₂I₂
Structural type	Tetragonal， I4/mmm space group
Lattice constant/Å	a=b=4.48， c=10.91	a=b=4.65， c=11.10	a=b=4.93， c=11.63
Density/（g·cm^-3）	7.180	7.307	7.702
Average atomic number	48.5	57.5	66.5
Band gap/eV	2.9	2.5	2.1
Resistivity/（Ω・cm）	—	—	6×10¹¹~2×10¹²
Light transmission range	Up to 80%@0.35~20 μm	Up to 75%@0.4 ~ 30 μm	Up to 55%@0.5~40 μm
Refractive index	n_o=1.898，n_e=2.444@20 μm	n_o=2.033，n_e=2.700 @30 μm	n_o=2.254，n_e=3.210@40 μm
Shear wave sound velocity along ［110］ direction/（m·s^-1）	347	273	254
Maximum acousto-optic quality factor/（s³·g^-1）	700×1.5×10^-18	2 600×1.5×10^-18	3 200×1.5×10^-18

图2 物理气相传输法生长的Hg2X2系列晶体。（a）Brimrose公司生长的Hg2Cl2、Hg2Br2和Hg2I2晶体［12］；（b）山东大学生长的Hg2Cl2和Hg2Br2晶体

Fig.2 Hg2X2 crystals grown by physical vapor transport method. （a） Hg2Cl2， Hg2Br2， and Hg2I2 crystals grown by Brimrose company［12］；（b） Hg2Cl2 and Hg2Br2 crystals grown by Shandong University

图3 基于Hg2Cl2晶体的格兰·泰勒棱镜［33］。（a）格兰·泰勒棱镜元件照片；（b）Hg2Cl2晶体透过率；（c）基于Hg2Cl2晶体的格兰·泰勒棱镜透过率

Fig.3 Glan-Taylor prism based on Hg2Cl2 crystals［33］. （a） Photograph of Glan-Taylor prism element；（b） transmittance of Hg2Cl2 crystal；（c） transmittance of Glan-Taylor prism based on Hg2Cl2 crystal

图4 基于Hg2Cl2晶体的偏振合束器［33］。（a） PBC照片；（b）镀红外抗反射膜的PBC对p偏振光和s偏振光的合束输出功率及合束效率；（c）镀红外抗反射膜的PBC的光束质量及光斑强度分布

Fig.4 Polarization beam combiner based on Hg2Cl2 crystal［33］. （a） Photograph of PBC；（b） beam-combined output power and combining efficiency of PBC coated with infrared antireflective film for p- and s-polarized lights；（c） beam quality and spot intensity distribution of PBC coated with infrared antireflective film

图5 Hg2X2晶体核辐射探测器能量分辨率［5］。（a）3 mm准半球型Hg2I2探测器对241Am的能量分辨率；（b）2 mm平面型Hg2I2探测器对662 keV γ射线的137Cs的能量分辨率；（c）尺寸为20 mm×10 mm×6 mm的像素型Hg2Br2探测器在1 000 V偏压下的能量分辨率

Fig.5 Energy resolution of Hg2X2 crystal nuclear radiation detectors［5］. （a） Energy resolution of 3 mm quasi-spherical Hg2I2 detector for 241Am；（b） energy resolution of 2 mm planar Hg2I2 detector for 662 keV gamma rays from 137Cs；（c） energy resolution of 20 mm×10 mm×6 mm pixelated Hg2Br2 detector under bias voltage of 1 000 V

图6 基于Hg2Br2晶体的α粒子闪烁体探测器［46］。（a）探测器结构；（b）对水中α粒子的光谱响应

Fig.6 α-particle scintillation detector based on Hg2Br2 crystal［46］. （a） Detector structure；（b） spectral response of α-particles in water

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