Search for: All records

Recently, there has been considerable interest in x-ray and gamma ray detectors with large volume and high energy resolution that operate at room temperature. To improve detector energy resolution, the carrier mobility-lifetime product needs to be increased, and the electronic trap state concentration needs to be minimized. Defect concentrations in the part per billion range can alter the charge transport and carrier recombination lifetime. In this work, thermally stimulated current spectroscopy measurements were systematically carried out in bulk halide perovskite single crystals of CsPbBr3 over a temperature range of 80–320 K. The origins and trap parameters of CsPbBr3 crystals from the solution growth and melt growth procedures were determined and compared. Trap concentrations were ranged from 1 × 1011 to 1 × 1016 cm−3. Appreciable detector performance was observed for CsPbBr3 crystals with trap concentrations less than 1 × 1014 cm−3. The comparison of spectral responses of crystal samples grown using two different methods shows that, after purification, solution-grown crystals are comparable to melt-grown crystals in terms of low defect concentration and improved detector performance. For an improved mobility-lifetime product and enhanced spectral response to high energy radiation from fissile materials, trap states in either type of a crystal ingot must be reduced closer to 1011 cm−3.

Room temperature semiconductor detector (RTSD) materials for γ‐ray and X‐ray radiation are in great demand for the nonproliferation of nuclear materials as well as for biomedical imaging applications. Halide perovskites have attracted great attention as emerging and promising RTSD materials. In this contribution, the material synthesis, purification, crystal growth, crystal structure, photoluminescence properties, ionizing radiation detection performance, and electronic structure of the inorganic halide perovskitoid compound TlPbI₃are reported on. This compound crystallizes in the ABX₃non‐perovskite crystal structure with a high density ofd = 6.488 g·cm^–3, has a wide bandgap of 2.25 eV, and melts congruently at a low temperature of 360 °C without phase transitions, which allows for facile growth of high quality crystals with few thermally‐activated defects. High‐quality TlPbI₃single crystals of centimeter‐size are grown using the vertical Bridgman method using purified raw materials. A high electrical resistivity of ≈10¹² Ω·cm is readily obtainable, and detectors made of TlPbI₃single crystals are highly photoresponsive to Ag K_αX‐rays (22.4 keV), and detects 122 keV γ‐rays from⁵⁷Co radiation source. The electron mobility‐lifetime productµ_eτ_ewas estimated at 1.8 × 10^–5cm²·V^–1. A high relative static dielectric constant of 35.0 indicates strong capability in screening carrier scattering and charged defects in TlPbI₃.

The wide‐bandgap, semiconducting ternary compound Hg₃Se₂I₂has shown promise as room‐temperature hard‐radiation detector. Since this compound was first reported, there has been significant improvement in crystal growth using a chemical vapor transport method with a polyethylene growth agent. To study the effects of this additional precursor on crystal quality, the nature of radiative and nonradiative defects using photoluminescence (PL) and photocurrent (PC) studies of Hg₃Se₂I₂single crystals are investigated. In contrast to earlier studies, excitation intensity‐dependence of PL emission shows that the near‐band‐edge (NBE) emission bands are all excitonic in nature. The PL intensity decreases with increasing temperature, with the higher energy peaks quenching by 40 K and the deeper levels quenched after 110 K. The PC spectra show a complex structure at room temperature related to NBE transitions in the band structure, while at low temperature only the direct gap transition is observed due to phonons freezing out. The PC spectra at low temperature also indicate several midgap levels that are attributed to native defects within the bulk crystal. These results indicate that the high quality of Hg₃Se₂I₂single crystals is maintained when the transport agent is used during growth, although there are still a variety of defects present.