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首页> 外文期刊>Nuclear instruments and methods in physics research >Material defect study of thallium lead iodide (TlPbI_3) crystals for radiation detector applications
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Material defect study of thallium lead iodide (TlPbI_3) crystals for radiation detector applications

机译：radiation探测器中碘化lead（TlPbI_3）晶体的材料缺陷研究

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TlPbI_3 is a promising semiconductor material for fabricating room-temperature radiation detectors, which have wide applications in national security, medical imaging, astrophysics research, industrial process monitoring and environmental survey. TlPbI_3 has a large energy bandgap at 2.3 eV, a high density (6.04 g/cm~3) and high concentrations of the high atomic number elements Tl and Pb. Such physical properties offer great potential to use TlPbI~3 to detect gamma-ray at room temperature with high detection efficiency. In this work, we used the positron annihilation lifetime spectroscopy (PALS) measurement and infrared transmission microscopy to study the material defects in bulk TlPbI~3 crystals. These crystals were grown with Bridgman method. For the PALS measurements, we used the positron experimental setup at North Carolina State University's PULSTAR reactor facility. A 15 μCi Na-22 positron source sealed with 7.6 μm thick Kapton films was sandwiched between two identical pieces of TlPbI_3 samples. Two cylindrical plastic scintillators (1 inch diameter by 1 inch long) combined with Hamamatsu H3378-50 photomultiplier tubes (PMT) were used to detect the 1.27 MeV gamma-rays in coincidence with the 511 keV annihilation gamma-rays as the start and the stop signals, respectively. A LeCroy Wavepro 7300A digital oscilloscope was used to digitize the raw PMT pulses and acquire the PALS spectra. The dominating positron lifetime in TlPbI3 is 393 ps and its intensity is more than 92%. This component is typically attributed to some vacancy type (or more likely, vacancy cluster) positron trapping sites. The first component of ～ 140 ps could be related to mono-vacancies or positrons annihilate in a delocalized lattice state. Compared with MAPbI_3, the higher average lifetime, τ_(av), and the higher intermediate lifetime (τ2) in TlPbI_3 indicate the presence of more anion-type vacancies and imply an increase in ionic conductivity. Using infrared transmission microscopy, we also observed the formation of large volume TlPbI_3 single crystal even in the transition portion between the conical seeding pocket and the normal growth chunk.
机译：TlPbI_3是用于制造室温辐射探测器的有前途的半导体材料，在国家安全，医学成像，天体物理学研究，工业过程监控和环境调查中具有广泛的应用。 TlPbI_3在2.3 eV具有大的能带隙，高密度（6.04 g / cm〜3）和高浓度的高原子序数元素Tl和Pb。这样的物理性质为使用TlPbI〜3在室温下以高检测效率检测伽马射线提供了巨大的潜力。在这项工作中，我们使用正电子an没寿命光谱（PALS）测量和红外透射显微镜研究了块状TlPbI〜3晶体的材料缺陷。这些晶体用布里奇曼法生长。对于PALS测量，我们使用了北卡罗莱纳州立大学PULSTAR反应堆设施中的正电子实验装置。用7.6μm厚的Kapton膜密封的15μCiNa-22正电子源夹在两个相同的TlPbI_3样品之间。使用两个圆柱形塑料闪烁体（直径1英寸长1英寸长）与Hamamatsu H3378-50光电倍增管（PMT）结合使用，以检测1.27 MeV伽马射线，同时将其作为511 keV ni灭伽马射线的起点和终点信号。 LeCroy Wavepro 7300A数字示波器用于数字化原始PMT脉冲并获取PALS光谱。 TlPbI3中主要的正电子寿命为393 ps，其强度大于92％。此成分通常归因于某些空位类型（或更可能是空位簇）正电子捕获位点。 〜140 ps的第一部分可能与单空位或正电子an灭在离域晶格状态有关。与MAPbI_3相比，TlPbI_3中的平均寿命τ_（av）较高，中间寿命（τ2）较高，表明存在更多的阴离子型空位，这意味着离子电导率增加。使用红外透射显微镜，我们还观察到即使在锥形种子袋和正常生长块之间的过渡部分中也形成了大体积的TlPbI_3单晶。

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