An Unusual Crystal Growth Method of the Chalcohalide Semiconductor, β-Hg₃S₂Cl₂: A New Candidate for Hard Radiation Detection

Abstract

We assess the mercury chalcohalide compound, β-Hg3S2Cl2, as a potential semiconductor material for X-ray and γ-ray detection. It has a high density (6.80 g/cm3) and wide band gap (2.56 eV) and crystallizes in the cubic Pm3̅n space group with a three-dimensional structure comprised of [Hg12S8] cubes with Cl atoms located within and between the cubes, featuring a trigonal pyramidal SHg3 as the main building block. First-principle electronic structure calculations at the density functional theory level predict that the compound has closely lying indirect and direct band gaps. We have successfully grown transparent, single crystals of β-Hg3S2Cl2 up to 7 mm diameter and 1 cm long using a new approach by the partial decomposition of the quaternary Hg3Bi2S2Cl8 compound followed by the formation of β-Hg3S2Cl2 and an impermeable top layer, all happening in situ during vertical Bridgman growth. The decomposition process was optimized by varying peak temperatures and temperature gradients using a 2 mm/h translation rate of the Bridgman technique. Formation of the quaternary Hg3Bi2S2Cl8 followed by its partial decomposition into β-Hg3S2Cl2 was confirmed by in situ temperature-dependent synchrotron powder diffraction studies. The single crystal samples obtained had resistivity of 1010 Ω·cm and mobility-lifetime products of electron and hole carriers of 1.4(4) × 10–4 cm2/V and 7.5(3) × 10–5 cm2/V, respectively. Further, an appreciable Ag X-ray photoconductivity response was observed showing the potential of β-Hg3S2Cl2 as a hard radiation detector material.

Defect Antiperovskite Compounds Hg3Q2I2 (Q = S, Se, and Te) for Room-Temperature Hard Radiation Detection

“…The bandgaps of Hg 3 Q 2 I 2 are smaller than the bromides and chlorides, while Hg 3 Q 2 X 2 (Q = S, Se, Te; X = Cl, Br) tends to be larger than 2.50 eV. ,, A smaller bandgap is preferable for better intrinsic energy resolution, due to a smaller intrinsic electron–hole pair generation energy ε …”

“…The bandgaps of Hg 3 Q 2 I 2 are smaller than the bromides and chlorides, while Hg 3 Q 2 X 2 (Q = S, Se, Te; X = Cl, Br) tends to be larger than 2.50 eV. 39,60,61 A smaller bandgap is preferable for better intrinsic energy resolution, due to a smaller intrinsic electron−hole pair generation energy ε. 6 Under SEM and AFM examinations, we observed parallel strips of stepwise terraces near the edge of the cleaved surfaces of Hg 3 S 2 I 2 , Hg 3 Se 2 I 2 , and Hg 3 Te 2 I 2 (Figure 5).…”

Intriguing Structural Transition Inducing Variable Birefringences in ABa2MS4Cl (A = Rb, Cs; M = Ge, Sn)

“…Mixed-anion compounds are of great significance in potential civil and military applications because of their structural diversities and unique physicochemical performances. − For instance, a series of borate halides and carbonate halides have been verified as excellent ultraviolet (UV)/deep-ultraviolet nonlinear-optical (NLO) candidates owing to their wide band gaps and impressive NLO coefficients. − Recently, introducing the highly electronegative halogen anions into the chalcogenides leads to the discovery of anion-mixed chalcohalides. − Investigation of their structures shows that highly electropositive elements (alkali, alkaline-earth, and rare-earth metals) are always linked with chalcogens and halogens to form strong ionic bonds, while other p-block elements are exclusively connected with chalcogens, generating stable covalent bonds. Such coordination modes of fundamental building units make the chalcohalides acquire interesting structures and fascinating properties. − Crystallogens have a strong tendency to form tetrahedral units with chalcogens that exist in the structure in various combination modes, such as isolated, , dimer, adamantine, one-dimensional chain, − and so forth. − Drawing halogens into thiogermanates and thiostannates has been developed as an efficient method to prepare the new chalcohalide compounds, and numerous examples have been discovered, such as NaBa 4 Ge 3 S 10 Cl, NaBa 2 SnS 4 Cl, Ba 4 Ge 3 S 9 Cl 2 , LaCa 2 GeS 4 Cl 3 , Ag 6 GeS 4 Cl 2 , and so forth.…”

Controlling the Vapor Transport Crystal Growth of Hg3Se2I2 Hard Radiation Detector Using Organic Polymer

“…On the basis of the concept of lattice hybridization, mercury chalcohalides Hg 3 Q 2 X 2 (Q = S, Se, and Te; X = Cl, Br, and I) have been proposed as a promising group of semiconductors for X- and γ-ray radiation detection at room temperature. − Among them, Hg 3 Se 2 I 2 with a high effective atomic number ( Z eff = 71.8) has demonstrated the most promising properties. Hg 3 Se 2 I 2 possesses a so-called “defect anti-perovskite structure” and fulfills the necessary properties of a semiconductor detector material, with a large bandgap (2.12 eV), high density (7.38 g/cm 3 ), high intrinsic resistivity (>10 12 Ω-cm), and high electron mobility (∼100 cm 2 ·V –1 ·s –1 ), which is comparable to that of detector-grade HgI 2 detectors. , The detectors based on as-grown Hg 3 Se 2 I 2 single crystals yielded resolved 241 Am α particle spectrum and 241 Am γ-ray spectrum; however, the single crystal size that can be grown is still limited …”