RII Track-4: The distribution and origin of deep level charge trapping centers in large size high-purity germanium crystals

天体物理学的最新发现彻底改变了我们对物质和宇宙的基本性质的理解，然而许多谜团依然存在。对引力现象的天文观测表明，宇宙中80%的物质是由暗物质(DM)组成的；然而，这种被提出的物质尚未被直接观测到。目前研究DM的方法依赖于对原子基本结构的复杂分析；然而，这些分析受到现有工具固有限制的阻碍。通过与田纳西大学的合作，PI将获得能够更好地了解这些限制的仪器，预计这将导致能够观察DM的仪器的开发取得重大进展。该项目将为国际和平研究所提供培训，为其未来职业发展建立必要的合作关系，并将加强国际和平研究所的总部机构南达科他大学和田纳西大学在半导体材料研究方面的伙伴关系。技术描述高纯锗(HPGe)晶体具有更大的体积与表面比，用于收集信号，特别是来自DM和0&amp；#946；&amp；#946；&amp；衰变的信号。到目前为止，大直径(10 Cm)HPGe晶体中的深能级电荷俘获中心还没有得到很好的研究。由于HPGe晶体中的深能级杂质对电荷的俘获，HPGe探测器能量分辨率的下降是基于Ge的DM和O&amp；的衰变研究的一大障碍。这项提议的目的是研究南达科他大学生长的大尺寸HPGe晶体中深能级电荷俘获中心的分布和来源，以用于未来吨级的衰变搜索实验。PI将与田纳西大学合作，利用深能级瞬变光谱(DLTS)研究HPGe晶体中电荷捕获中心的分布和来源，其中包括铜、铜-氢络合物、双空位氢和未知缺陷。这些结果将有助于PI设计适当的方法，在获奖期后的提纯和晶体生长中减少电荷捕获中心的水平。由此产生的具有较低电荷捕获中心的大尺寸HPGe晶体将是低本底实验的理想材料，特别是那些寻找DM和0&amp；&amp；衰变的实验。

Non-technical DescriptionRecent discoveries in astrophysics have revolutionized our understanding of the fundamental nature of matter and the cosmos, yet many mysteries remain. Astronomical observations of gravitational phenomena indicate that 80% of the matter in the universe is composed of dark matter (DM); however, this proposed material has not yet been directly observed. Current approaches to the study of DM rely on sophisticated analyses of the fundamental structure of atoms; however, these analyses are hindered by inherent limitations of the instruments that are currently available. Through a collaboration with the University of Tennessee, the PI will have access to instrumentation that will provide a greater understanding of these limitations, and it is expected that this will lead to significant advancements in development of instruments capable of observing DM. This project will provide training for the PI, establish needed collaborations for future development of his career, and will strengthen the partnership between the PI's home institution of the University of South Dakota and the University of Tennessee in research on semiconductor materials. Technical Description High-Purity Germanium (HPGe) crystals have larger volume-to-surface ratios for collecting signal, in particular from DM and 0νββ decay. Up to now, deep-level charge-trapping centers have not been well studied in large diameter (10 cm) HPGe crystals. Due to charge trapping by deep-level impurities in the HPGe crystals, the degradation of energy resolution of HPGe detectors is a large obstacle for germanium-based DM and 0νββ decay search experiments. The goal of this proposal is to study the distribution and origin of deep-level charge-trapping centers in large size HPGe crystals grown by the University of South Dakota for future ton-scale 0νββ decay search experiments. With the collaboration of the University of Tennessee, the PI will study the distribution and origin of charge-trapping centers in HPGe crystals, which include copper, copper-hydrogen complexes, di-vacancy hydrogen and unknown defects, by Deep Level Transient Spectroscopy (DLTS). The results will help the PI to design appropriate methods of reducing the level of charge-trapping centers in purification and crystal growth beyond the award period. The resulting large size HPGe crystals with lower charge-trapping centers will be an ideal material for low background experiments, especially those searching for DM and 0νββ decay.