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

The high Z chalcohalides Hg(3)Q(2)I(2) (Q = S, Se, and Te) can be regarded as of antiperovskite structure with ordered vacancies and are demonstrated to be very promising candidates for X- and gamma-ray semiconductor detectors. Depending on Q the ordering of the Hg vacancies in these defect antiperovskites varies and yields a rich family of distinct crystal structures ranging from zero-dimensional to three-dimensional, with a dramatic effect on the properties of each compound. All three Hg(3)Q(2)I(2) compounds show very suitable optical, electrical, and good mechanical properties required for radiation detection at room, temperature. These compounds possess a high density (>7 g/cm(3)) and wide bandgaps (>1.9 eV), showing great stopping power for hard radiation and high intrinsic electrical resistivity, over 10(11) Omega cm. Large single crystals are grown using the vapor transport method, and each material shows excellent photo sensitivity under energetic photons. Detectors made from thin Hg(3)Q(2)I(2) crystals show reasonable response under a series of radiation sources, including Am-241 and Co-57 radiation. The dimensionality of Hg-Qmotifs (in terms of ordering patterns of Hg vacancies) has a strong influence on the conduction band structure, which gives the quasi one-dimensional Hg3Se2I2 a more prominently dispersive conduction band structure and leads to a low electron effective mass (0.20 m(0)). For Hg3Se2I2 detectors, spectroscopic resolution is achieved for both Am-241 a particles (5.49 MeV) and Am-241 gamma-rays (59.5 keV), with full widths at half-maximum (FWHM, in percentage) of 19% and 50%, respectively. The carrier mobility-lifetime tr product for Hg(3)Q(2)I(2) detectors is achieved as 10(-5)-10(-6) cm(2)/V. The electron mobility for Hg3Se2I2 is estimated as 104 +/- 12 cm(2)/(V.s). On the basis of these results, Hg3Se2I2 is the most promising for room temperature radiation detection.