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

该项目致力于镉锌碲的晶体生长，这是一种通过检测发射的伽马射线来监测放射性材料的便携式、低成本和灵敏的手段。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，基于碲化锌镉的伽马探测器具有独特的优点：1.碲锌镉探测器是一种直接探测器，因此允许设计小型探测探测器和便携式设备。2.器件工作在室温下，避免了冷却技术。3.由于与NaI探测器相比，镉锌Te探测器的分辨率要高得多，因此它们是唯一的室温探测器，允许手持和便携式设备检测显著的铅或钢屏蔽层后面的放射性信号。寻求低成本、大面积、成分变化小、电学性能均匀的单晶。目前，大尺寸单晶的生长是通过布里奇曼方法完成的，这是出了名的困难。这些晶体通常表现出相当差的结晶完备性、大量的大缺陷和较差的锌浓度均匀度。本项目的目标是应用大规模的数值模拟来评估一种替代的生长方式--不稳定的垂直布里奇曼结构，而不是经典的稳定结构。虽然这种新的生长技术与直觉和探索性相反，但它可能会显著提高CdZnTe衬底的质量和工艺产量，并提供对大块晶体生长过程的新理解。该项目解决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，重点是研究和教育的融合。该项目通过让学生接触到对国家安全至关重要的技术问题，帮助发展科学队伍。其他更广泛的影响包括与ACT计划的相关性以及在核医学成像设备、数字射线照相和高分辨率天体物理成像方面的潜在进展。此外，从这个项目中学到的理解也将适用于通过布里奇曼方法生长其他晶体材料。该奖项由美国国家科学基金会和情报界共同支持。数学和物理科学局的反恐方法(ACT)方案支持基础研究和劳动力发展方面的新概念，有可能为国家安全作出贡献。

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.