GaN High-Electron-Mobility Transistors have gained some foothold in the power-electronics industry. This is due to wide frequency bandwidth and power handling. Gallium Nitride offers a wide bandgap and higher critical field strength compared to most wide-bandgap semiconductors, resulting in better radiation resistance. Theoretically, it supports higher speeds as the device dimensions could be reduced without suffering voltage breakdown. The simulation and experimental results illustrate the superior performance of the Gallium Nitride High-Electron-Mobility Transistors in an amplifying circuit. Using a spice model for commercially available Gallium Nitride High-Electron-Mobility Transistors, non-distorted output to an input signal of 200 ps was displayed. Real-world measurements underscore the fast response of the Gallium Nitride High-Electron-Mobility Transistors with its measured slew rate at approximately 3000 V/μs, a result only 17% lower than the result obtained from the simulation. This fast response, coupled with the amplifier radiation resistance, shows promise for designing improved detection and imaging circuits with long Mean Time Between Failure required, for example, by next-generation industrial-process gamma transmission-computed tomography.

The material family halide perovskites has been critical in recent room-temperature radiation detection semiconductor research. Cesium lead bromide (CsPbBr3) is a halide perovskite that exhibits characteristics of a semiconductor that would be suitable for applications in various fields. In this paper, we report on the correlations between material purification and crystal material properties. Crystal boules of CsPbX3 (where X = Cl, Br, I, or mixed) were grown with the Bridgman growth method. We describe in great detail the fabrication techniques used to prepare sample surfaces for contact deposition and sample testing. Current–voltage measurements, UV–Vis and photocurrent spectroscopy, as well as photoluminescence measurements, were carried out for material characterization. Bulk resistivity values of up to 3.0 × 109 Ω∙cm and surface resistivity values of 1.3 × 1011 Ω/□ indicate that the material can be used for low-noise semiconductor detector applications. Preliminary radiation detectors were fabricated, and using photocurrent measurements we have estimated a value of the mobility–lifetime product for holes (μτ)h of 2.8 × 10−5 cm2/V. The results from the sample testing can shed light on ways to improve the crystal properties for future work, not only for CsPbX3 but also other halide perovskites.

Elpasolite scintillators show great promise for dual mode neutron-gamma radiation detection and imaging but the impact of high dose radiation on performance characteristics has not been evaluated. Crystalline (Cs,Tl)(2)LiLaBr6:Ce (CTLLB) materials are grown. After growth the 1-inch diameter crystals are processed and packaged. Prior to the irradiation sequence at SRNL, the detector performance of the encapsulated crystal is measured with gamma-ray check sources including Cs-137 and Eu-152. Properties such as energy resolution, light yield, proportionality behavior, and decay times are measured. The packaged crystal is irradiated four times at dose rates of 1, 10, 100 and 1,000 Gy of absorbed dose in a Co-60 irradiation and the performance of the crystal is evaluated before and after each radiation treatment. Cumulative dose rates between irradiation were 1, 11, 111 and 1,111 Gy. Initial results show a decreased measured light yield after each radiation exposure, however further analysis on the packaging materials will be pursued.

In this paper we will present the latest growth and characterization of CsPbX 3 crystals for room temperature gamma-ray detection and imaging. Material purification, synthesis, crystal growth from $16-\mathrm{mm}$ to $35-\mathrm{mm}$ diameter, sample preparation, and detector characterization will be presented. We have managed to grow single crystals, free of polarized planes, with resistivity $\gt$ $6.0 \times 10^{9} \Omega$-cm and $\mathrm{mt}_{\mathrm{h}}\gt2.0 \times 10^{-4} \mathrm{~cm}^{2} / \mathrm{V}$.

In this paper we are reporting on the progress and scale up of the Cerium-doped Tl2LiYCl6 (TLYC) scintillator. The boules up to 2-inch in diameter were grown by the Bridgman method at Fisk University. The lapped and polished samples were characterized for their scintillation properties including gamma-neutron dual mode detection. The 1.5-inch diameter samples demonstrated the energy resolution as good as 4.5% (FWHM) at 662 keV. The neutron peak due to 6Li(n, α) reaction was observed at 1.8 MeV gamma equivalent energy. Gamma-neutron pulse shape discrimination (PSD) was demonstrated with the Figure-of-Merit (FOM) of 1.8. The hermetically encapsulated samples were also evaluated for their radiation hardness with irradiation up to 1 Mrad.

We are reporting on the growth and performance of co-doped Tl 2 LiYCl 6 (TLYC) crystals grown by the Bridgman method at Fisk University. In recent years cerium doped TLYC has emerged as a promising dual-mode scintillation detector material for many defense and homeland security applications. For the past few years Fisk University has successfully grown and produced large diameter (≥ 1-inch diameter) TLYC:Ce crystals with consistent growth yield and scintillation performance. Good gamma-ray energy resolution as well as good neutron-gamma pulse height discrimination (PSD) are regularly obtained. We have recently started to grow co-doped TLYC crystals in an attempt to further improve growth and scintillation properties.16-mm diameter TLYC crystals co-doped with lanthanides and alkali metal halides have been grown and characterized. A sample sent to Radiation Monitoring Devices, Inc. for neutron-gamma PSD measurement results in a figure of merit better than that of TLYC:Ce. Characterization results from the growth of large diameter TLYC crystal co-doped with lanthanides and alkali metal halides, as well as radiation tolerance of packaged co-doped TLYC crystal, will be presented.

This paper covers the successful growth and characterization of large diameter dual mode Tl2LiYCl6:Ce (TLYC) scintillation crystals. Single, transparent ∅1.5" TLYC crystals are grown by the Bridgman melt growth method at Fisk University. Characterization of TLYC scintillation crystals, such as measurements of light yield, energy resolutions, luminescence decay times, gamma-neutron pulse height discrimination, as well as radiation tolerance are done at Fisk University, as well as collaborators’ sites. Characterization results are reported in this paper.

We will present an equipment design and technique to produce inorganic halide ceramic scintillators Cs2HfCl6 (CHC) and Tl2HfCl6 (THC). Also presented is initial ceramic processing for compounds with non-congruent melts: elpasolite Tl2LiLaBr6 (TLLB) and Li-based halide Eu-doped LiSr2I5 (LSI). Comparison between the crystal results from the melt growth method and the ceramic fabrication will be presented. Improvements and optimization of CHC and THC ceramic scintillator fabrication are gauged by monitoring the energy resolution and peak position of 137Cs full energy peak at 662 keV. Both ceramic CHC and THC scintillators have similarly good proportionality compared to their single crystal counterparts.

Elpasolite scintillators play an important role in radiation detection and imaging. Novel Tl-based elpasolite scintillators such as Ce-doped Tl2LiYCl6 (TLYC) have been developed as excellent Tl-based dual mode gamma and neutron detectors. This paper presents a successful high yield growth and gamma-ray characterization of large diameter (1-inch to 1.5-inch diameter) single, crack-free, and transparent TLYC crystals at Fisk University. Energy resolution of 4.2% (FWHM) at 662 keV and light yield of 26,000 photons/MeV are measured. As-processed and hermetically packaged TLYC samples are characterized for their gamma-ray energy resolutions, light yields, non proportionality behaviors and decay times. Successful growth of 1-inch diameter (Cs,Tl)(2)LiLaBr6:Ce crystals are also shown. The best result is obtained when the content of Cs+ is larger than Tl+. Energy resolution of 3.4% (FWHM) at 662 keV is measured for (Cs,Tl)(2)LiLaBr6:Ce for 75% Cs-to-25% Tl ratio.

Professor Jurchescu, Dr. Wolszczak, Professor Burger, Dr. Bourret-Courchesne, and Professor Dorenbos introduce the Journal of Materials Chemistry C – Materials Advances themed collection in memoriam of Prof. Richard T. Williams.

Nuclear and high energy physics research has a need for new, high performance scintillators with high light yields; high densities, fast decay times, and are radiation hard. In this paper we present crystal growth and results from 16-mm diameter cerium (Ce)-doped Tl2LaCl5 (TLC) and europium (Eu)-doped TlCa2Br5(TCB) as well as one-inch diameter cerium-doped Tl2GdBr5 (TGB) and europium-dopedTlSr2I5 (TSI), each grown in a two-zone vertical furnace by the modified Bridgman method. Samples extracted and processed from the grown boule are characterized for their scintillation properties like energy resolution, light yield, decay time and non-proportionality.Energy resolution (FWHM) at 662 keV of 5.1 and TSI, respectively. Ce-doped TGB and TLC have single decay time components of 26 ns and 48 ns, respectively, while Eu-doped TCB and TSI have long decay times with primary decay constants of 571 ns and 630 ns. These compounds exhibit good proportionality behavior when compared toNaI:Tl and BGO.

This paper describes the synthesis, crystal growth, detector fabrication, radiation hardening studies, MCNP modeling, and characterization of lithium indium diselenide or LiInSe2. This newly-developed roomtemperature thermal neutron detector has semiconducting and scintillating properties and it is suitable for neutron detection application. LiInSe2 was synthesized starting from elemental Li, In, Se in two steps due to high reactivity of Li. A single crystal of LiInSe2 was grown using the Vertical Bridgman method. The room temperature band gap was found to be 2.8 eV using optical absorption measurements. Bulk resistivity was measured at similar to 5 x 10(11) Omega cm. Photoconductivity measurements of LiInSe2 wafers identified a peak in the photocurrent around 445 nm. Nuclear radiation detectors were fabricated from single crystal wafer and the responses to alpha particles at various biases were measured. The mobility-lifetime product was estimated. Gamma irradiation studies were performed with calculated absorbed doses ranging from 0.2126 to 21,262 Gy. The characterization of the two wafers for their scintillator performance was conducted after each irradiation. The gamma irradiation produced a reduction of the light yield that translated to a lower channel number for the centroid of alpha detection spectra. It also showed a considerable reduction of the decay time after the first irradiation. These are the first studies on gamma radiation hardening with this material.

Single crystal scintillators have become one of the most common materials used in technologies that use radiation detectors. Unfortunately, as technology demands improved detectors, research into better single crystal scintillators has nearly reached its limit. Ceramics provide many benefits over single crystal scintillators and have emerged as a promising new production process. Recent research into ceramic scintillators has mostly dealt with oxides as they are relatively easy to handle and are typically non‐hygroscopic. Among single crystal scintillators, a trend has emerged indicating that the addition of halide ions into the crystal structure improves the light yield and energy resolution of the scintillation material but also tends to make the material hygroscopic and in some cases intrinsically radioactive. Little research is devoted to the investigation of undoped halide ceramic scintillators. Transparent halide Cs 2 HfCl 6 ceramics are developed by hot uniaxial pressing, and the scintillation properties are compared to that of its single crystal counterpart. The energy resolution of the ceramic is found to be 6.4% at 662 keV. The initial results indicate that ceramic scintillators are a viable alternative and a promising new direction in scintillator material technology.

This paper reports on the performance of the inorganic scintillator caesium hafnium chloride (CHC) under exposure to the mixed radiation field of an AmBe neutron source and coupled to a silicon photomultiplier (SiPM). The neutron response is determined using the pulse shape discrimination charge comparison technique which can clearly identify both the (n,α) and (c) reactions in the material. Figures of merit for the pulse shape discrimination are presented and the quenching of the different channels is assessed through comparison to Monte Carlo simulations.

Nuclear and high energy physics research has a need for new, high performance scintillators with high light yields, high densities, fast decay times, and radiation hardness. In this paper we present crystal growth and results from 16-mm diameter cerium (Ce)-doped Tl2LaCl5 (TLC) and europium (Eu)-doped TlCa2Br5 (TCB) as well as one-inch diameter cerium-doped Tl2GdBr5 (TGB) and europium-doped TlSr2I5 (TSI), each grown in a two-zone vertical furnace by the modified Bridgman method. Samples extracted and processed from the grown boule are characterized for their scintillation properties like energy resolution, light yield, decay time and non-proportionality. Energy resolution (FWHM) at 662 keV of 5.1%, 3.4%, 4.0%, and 3.3% are obtained for samples of TGB, TLC, TCB, and TSI, respectively. Ce-doped TGB and TLC have single decay time components of 26 ns and 48 ns, respectively, while Eu-doped TCB and TSI have long decay times with primary decay constants of 571 ns and 630 ns? These compounds exhibit good proportionality behavior when compared to NaI:Tl and BGO.

The mid-infrared fluorescence properties of erbium (Er) doped low-phonon ternary chloride-based crystals (KPb2Cl5, Cs2HfCl6, CsPbCl3, CsCdCl3) have been investigated. All crystals were grown by vertical Bridgman technique. Following optical excitations at 805 nm and 660 nm, all Er3+ doped chlorides exhibited infrared emissions at ~2750, ~3500, and ~4500 nm at room temperature. The mid-infrared emission at 4500 nm originating from the 4I9/2 → 4I11/2 transition showed long emission lifetime values of ~7.8 ms and ~11.6 ms for Er3+ doped Cs2HfCl6 and CsCdCl3 crystals, respectively. In comparison, Er3+ doped KPb2Cl5 and CsPbCl3 demonstrated shorter lifetimes of ~3 ms and ~1.8 ms, respectively. The temperature dependence of the 4I9/2 decay times was performed for Er3+ doped CsPbCl3 and CsCdCl3 crystals. We observed that the fluorescence lifetimes were nearly independent of the temperature, indicating a negligibly small non-radiative decay rate through multiphonon relaxation, as predicted by the energy gap law for low phonon energy hosts. The room temperature stimulated emission cross-sections for the 4I9/2 → 4I11/2 transition were determined to be in a range of ~0.14-0.54 x 10-20 cm2 for the studied Er doped chloride crystals.

Research in ceramic scintillators has steadily progressed alongside the research in bulk single crystal scintillator growth. As interest in faster scintillation material production with lower cost increases, more research on scintillating ceramics is needed. Research targeting optimization of optically transparent ceramics that can rival bulk-grown crystals grown may lower cost, increase yield, increase volume, and improve energy resolution in applications and systems currently using sodium iodide and alike. Ceramic scintillators that are dense (>5 g/ cm3), have high effective Z (>60), are bright (>40,000 photons/MeV), and are not sensitive to moisture as well as those that can be handled without protection are desired. Ultra-fast ceramic materials are also of interest. This paper presents an equipment design and technique to produce inorganic halide ceramic scintillators Cs2HfCl6 (CHC) and Tl2HfCl6 (THC). Improvements and optimization of CHC and THC ceramic scintillator fabrication are gauged by monitoring the energy resolution and peak position of 137Cs full energy peak at 662 keV. With a 1-inch diameter CHC ceramic scintillator, energy resolution of 5.4% (FWHM) and light yield of 20,700 ph/MeV are achieved, while with a 16-mm diameter THC ceramic scintillator, energy resolution of 5.1% (FWHM) and light yield of 27,800 ph/MeV are achieved. Decay times of 0.6 mu s (21%) and 3.0 mu s (79%) are measured for CHC and 0.3 mu s (13%) and 1.0 mu s (87%) for THC. Both ceramic CHC and THC scintillators have similarly good proportionality data when compared to their single crystal counterparts.

In this paper the growth of a 16-mm diameter 5 wt-% Ce-doped Tl2NaYCl6 and its characterization as a gammaray detector are reported. With a 016 mm x 8 mm cylindrical sample, energy resolution of 4.1% (FWHM) at 662 keV and light yield of 27,800 ph/MeV are measured. Decay times of 91 ns (34%), 462 ns (52%), and 2.1 mu s (15%) are calculated. The x-ray excited emission spectrum exhibits bands that are similar to other Tl-based elpasolite scintillators like Tl2LiYCl6:Ce.

This paper reports on recently successful growths of single, transparent 1.5-inch diameter Cs2HfCl6 (CHC) and 1 inch diameter Tl2HfCl6 (THC) and Tl2ZrCl6 (TZC) scintillators crystals using the vertical Bridgman method as well as their radiometric and scintillation performance and properties. Energy resolution of 4.0% (FWHM) at 662 keV has been obtained for CHC and 4.1% and 4.2% for each THC and TZC respectively. This paper covers gamma-ray non-proportionality, light yield, and decay times for CHC, THC and TZC, respectively.