Deep levels of undoped GaTe and indium-doped GaTe crystals are reported for samples grown by the vertical Bridgman technique. Schottky diodes of GaTe and GaTe:In have been fabricated and characterized using current-voltage, capacitance-voltage, and deep-level transient spectroscopy ͑DLTS͒. Three deep levels at 0.40, 0.59, and 0.67 eV above the valence band were found in undoped GaTe crystals. The level at 0.40 eV is associated with the complex consisting of gallium vacancy and gallium interstitial ͑V Ga -Ga i ͒, the level at 0.59 eV is identified as the tellurium-on-gallium antisite ͑Te Ga ͒, and the last one is tentatively assigned to be the doubly ionized gallium vacancy ͑V Ga ء ͒. Indium isoelectronic doping is found to have noticeable impacts on reducing the Schottky saturation current and suppressing the densities of Te Ga and V Ga ء defects. The peak which dominated the DLTS spectrum of GaTe:In is assigned to be the defect complex consisting of V Ga and indium interstitial ͑In i ͒. Low-temperature photoluminescence ͑PL͒ spectroscopy measurements were performed on GaTe and GaTe:In crystals. A shallow acceptor level at 140 meV corresponding to V Ga was measured in undoped GaTe. Two shallow acceptor levels at 123 and 74 meV corresponding to V Ga and indium-on-gallium antisite In Ga were observed in GaTe:In samples. The PL results suggested that the indium atoms could occupy gallium vacant sites during GaTe crystal growth period and thereby change the electrical and optical properties of GaTe crystal.
Abstract. Strontium iodide doped with europium [SrI 2 ðEu2þ Þ] is a new scintillator material being developed as an alternative to lanthanum bromide doped with cerium [LaBr 3 ðCe 3þ Þ] for use in high-energy astrophysical detectors. As with all scintillators, the issue of nonproportionality is important because it affects the energy resolution of the detector. We investigate how the nonproportionality of SrI 2 ðEu 2þ Þ changes as a function of temperature from 16 to 60°C by heating the SrI 2 ðEu 2þ Þ scintillator separate from the photomultiplier tube. In a separate experiment, we also investigate the nonproportionality at high energies (up to 6 MeV) of SrI 2 ðEu 2þ Þ at a testing facility located at NASA Goddard Space Flight Center. We find that the nonproportionality increases nearly monotonically as the temperature of the SrI 2 ðEu 2þ Þ scintillator is increased, although there is evidence of nonmonotonic behavior near 40°C, perhaps due to electric charge carriers trapping in the material. We also find that within the energy range of 662 keV to 6.1 MeV, the change in the nonproportionality of SrI 2 ðEu 2þ Þ is ∼1.5 to 2%. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Strontium iodide doped with europium (SrI 2 :Eu 2+) is a new scintillator being developed for use in high-energy astrophysical detectors with excellent energy resolution. Nonproportionality is the primary limiting factor to improving its energy resolution, although the physics of nonproportionality is not yet fully understood. In the past few years, co-dopants have been used to alter nonproportionality. By irradiating a SrI 2 :Eu 2+ sample with a 2,255 Ci 137 Cs source, we explore both the crystal's potential for space-based applications in a radiation environment and this new method of altering nonproportionality. At ~6,200 Gy irradiation, a drop of 7.8% at 700 nm and a drop of 14.1% at 450 nm were seen in the transmission spectrum. Nonproportionality was also reduced after irradiation, shifting from 87% to 101% of the theoretical light yield at 32.1 keV, while the 4.7 keV peak decreased 40% closer to its theoretical value. We propose a novel method of altering the nonproportionality of scintillators, using radiation-induced F-centers in place of co-dopants.
Autistic adults experience significant unmet healthcare needs, with opportunities for improvement in both the systems and the practitioners who serve this population. Primary care physicians/practitioners (PCPs) are a natural choice to provide comprehensive care to autistic adults but often lack experience in serving this population. This pilot study developed and tested an Extension for Community Healthcare Outcomes (ECHO) Autism model adapted from our previous work, focused specifically on training PCPs in best‐practice care for autistic adults. The project was informed directly by the perspectives and preferences of autistic adults, caregivers, and PCPs. Two consecutive cohorts of PCPs participated in ECHO Autism Adult Healthcare sessions. Each cohort met 1 h twice a month for 6 months, with 37 PCPs (n = 20 in Cohort 1, and n = 17 in Cohort 2) participating. Based on findings from the first cohort, adjustments were made to refine the session preparation, curriculum, conduct of the ECHO, resources, and evaluation. After participation in the ECHO Autism program, PCP self‐efficacy and satisfaction improved, while the number of perceived barriers did not change. Knowledge did not improve significantly in Cohort 1, but after adjustments to the training model, participants in Cohort 2 showed significant knowledge gains. While attention to systems of care is critical to addressing barriers in healthcare in the autistic population, the ECHO Autism Adult Healthcare model is feasible and holds promise for improving PCP satisfaction and self‐efficacy in working with autistic adults.
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