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基本性质的理解，但仍有许多谜团。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，这种物质尚未被直接观测到。目前的DM研究方法依赖于对原子基本结构的复杂分析;然而，这些分析受到现有仪器固有局限性的阻碍。通过与田纳西大学的合作，PI将获得仪器，这将提供对这些限制的更好的理解，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PI提供培训，为他的职业生涯的未来发展建立必要的合作，并将加强PI的家乡南达科他州大学和田纳西大学之间在半导体材料研究方面的伙伴关系。技术说明 高纯度锗（HPGe）晶体具有较大的体积-表面比，用于收集信号，特别是来自DM和0的衰减。迄今为止，大直径（10 cm）HPGe晶体中的深能级电荷俘获中心尚未得到很好的研究。由于HPGe晶体中的深能级杂质的电荷俘获，HPGe探测器的能量分辨率的下降是锗基DM和0 #957;#946; #946;衰变搜索实验的一大障碍。本计划的目标是研究南达科他州大学生长的大尺寸HPGe晶体中深能级电荷俘获中心的分布和起源，以用于未来的吨级0 #957;#946;#946;衰变搜索实验。在田纳西大学的合作下，PI将通过深能级瞬态光谱（DLTS）研究HPGe晶体中电荷捕获中心的分布和起源，其中包括铜，铜-氢复合物，双空位氢和未知缺陷。研究结果将有助于PI设计适当的方法，以减少在纯化和晶体生长超出奖励期的电荷捕获中心的水平。所得到的具有较低电荷俘获中心的大尺寸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 #957;#946; #946;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.