ACT/SGER: Evaluation of a Novel Approach for Improved Growth of CdZnTe

该项目涉及碲锌镉晶体的生长，碲锌镉是一种可用作便携式、低成本和敏感手段的材料，通过探测发射的伽马射线来监测放射性材料。伽马探测器有几种技术，如经典的碘化钠（NaI）闪烁装置和液氮冷却的锗探测器。然而，基于碲锌镉（CdZnTe）的伽马探测器提供了独特的优势：1。CdZnTe作为直接检测器工作，从而允许设计小型检测探针和便携式设备。2. CdZnTe器件在室温下工作，因此避免了冷却技术。3.由于CdZnTe探测器具有比NaI探测器更好的分辨率，因此它们是唯一允许手持和便携式设备检测重要铅或钢屏蔽后面的放射性特征的室温探测器。寻求低成本、大面积、具有低组成变化和均匀电性能的单晶。目前，CdZnTe的大单晶的生长是通过布里奇曼方法完成的，并且是众所周知的困难。这些晶体通常表现出相当差的晶体完整性、大缺陷的显著浓度和差的Zn浓度均匀性。这个项目的目的是应用大规模的数值模拟，以评估一种替代的生长配置CdZnTe -一个不稳定的垂直布里奇曼配置，而不是经典的稳定配置。虽然违反直觉和探索，这种新的生长技术可以允许显着改善CdZnTe衬底质量和工艺产量，并提供了新的理解体晶体生长过程。该项目解决了与具有技术相关性的电子/光子材料相关的基础研究问题。该项目的一个重要特点是教育和培训，重点是研究与教育的结合。该项目通过让学生接触对国家安全至关重要的技术问题，帮助科学工作者的发展。其他更广泛的影响包括与ACT计划的相关性以及核医学成像设备、数字X射线照相和高分辨率天体物理成像的潜在进展。此外，从这个项目中学到的理解将适用于通过布里奇曼方法生长其他晶体材料。该奖项由NSF和情报界共同支持。数学和物理科学局的打击恐怖主义方法方案支持基础研究和劳动力发展方面的新概念，这些概念有可能促进国家安全。

This project addresses crystal growth of CdZnTe, a material useful as a portable, low-cost, and sensitive means to monitor radioactive materials via the detection of emitted gamma rays. There are several technologies for gamma detectors, such as classical sodium iodide (NaI) scintillation devices and liquid-nitrogen-cooled Germanium detectors. However, gamma detectors based on cadmium zinc telluride (CdZnTe) offer unique advantages: 1. CdZnTe operates as a direct detector, thereby allowing for the design of small detection probes and portable devices. 2. CdZnTe devices work at room temperature, thus avoiding cooling technology. 3. Since CdZnTe detectors have a much better resolution compared to NaI detectors, they are the only room temperature detectors that allow hand-held and portable devices to provide a detection of radioactive signatures behind significant lead or steel shieldings. Low cost, large-area, single crystals with low compositional variation and homogeneous electrical properties are sought. Currently, the growth of large, single crystals of CdZnTe is accomplished by the Bridgman method and is notoriously difficult. These crystals typically exhibit rather poor crystalline perfection, significant concentrations of large defects, and poor uniformity of Zn concentration. The objective of this project is to apply large-scale numerical simulation to assess an alternative growth configuration for CdZnTe - a destabilizing vertical Bridgman configuration rather than the classical stabilizing configuration. While counter intuitive and exploratory, this new growth technique may allow for dramatic improvements in CdZnTe substrate quality and process yields, and provides new understanding of bulk crystal growth processes. %%% The project addresses fundamental research issues associated with electronic/photonic materials having technological relevance. An important feature of the project is education and training, with emphasis on integration of research and education. The project aids in the development of the scientific workforce by exposing students to technical issues important for the security of the nation. Other broader impacts include relevance to the ACT program and potential advances in nuclear medical imaging devices, digital radiography, and high-resolution astrophysical imaging. Additionally, the understanding learned form this project will be applicable to the growth of other crystalline materials via the Bridgman method. This award is supported jointly by the NSF and the Intelligence Community. The Approaches to Combat Terrorism (ACT) Program in the Directorate for Mathematics and Physical Sciences supports new concepts in basic research and workforce development with the potential to contribute to national security.