Characterizing and Modifying Defects that Trap Excitons in Yttrium Aluminum Garnets Doped with Rare-Earth Elements

技术：该项目旨在更好地了解稀土掺杂的Y3+石榴石晶体中激子与晶体缺陷之间的相互作用。更深入地理解和控制激子动力学的方法是通过它们与激活杂质和晶格缺陷的相互作用。通过对晶格缺陷的类型、大小和浓度的全面研究，将使用正电子寿命谱来表征YAG结构中的晶格缺陷。正电子参数将与激子行为、光子发射和闪烁特性的光学测量相关联。正电子参数和光学性质之间的相关性将作为生长条件、稀土掺杂剂的选择、掺杂水平、化学计量比偏差和生长后处理的函数进行监测。在包括在不同气氛下的热退火的处理步骤之后，将进一步检查这种相关性。表征的结果将被用于修改合成和生长条件，以改善光学性能。非技术性：该项目解决与电子和光子学技术相关的材料科学专题领域的基础研究问题。通过更好地了解激子与缺陷的相互作用，这项研究有望显着提高闪烁体的性能。闪烁体材料将各种类型的辐射转化为光子，然后可以收集和分析。两个重要的应用领域是医疗诊断，以及伽马和中子辐射检测。晶体缺陷与闪烁体性能之间的关系是一个重要的课题，目前还没有得到很好的理解。这些研究的结果将有助于理解如何通过设计改进的闪烁体组合物和结构来提高闪烁体的效率。这项研究将加强对离子晶体中缺陷形成的了解，并选择改进的合成/处理方法以获得优异的光学性能。该项目将整合本科生和研究生参与者的研究和教育。培训将在基础和应用物理、材料科学、电子学和光子学的多学科环境中进行。除了为研究生提供支持和指导外，PI还将通过一个网站激励本科生和高中生，并在校园内外向学生发表演讲。私人投资机构将创建一个多元化的研究小组，其中包括妇女和少数群体成员。研究成果将通过主要期刊上的出版物以及在会议和研讨会上的陈述进行传播。

Technical: This project aims for greater understanding of the interactions between excitons and crystalline defects in rare earth doped yttrium aluminum garnet (YAG) scintillator crystals. The approach toward more in-depth understanding and control of exciton dynamics is through their interactions with activating impurities and lattice defects. Lattice defects in the YAG structure will be characterized using positron lifetime spectrometry through a comprehensive study of their types, sizes and concentrations. Positron parameters will be correlated with optical measurements of exciton behavior, photon emission, and scintillation properties. The correlation between positron parameters and optical properties will be monitored as a function of growth conditions, choice of rare-earth dopant, doping levels, deviations from stoichiometry and postgrowth treatments. The correlation will further be examined following processing steps that include thermal annealing under different atmospheres. Results of the characterizations will be used to modify synthesis and growth conditions in order to improve optical properties. Non-technical: The project addresses basic research issues in a topical area of materials science with technological relevance in electronics and photonics. Through greater understanding of the interactions of excitons with defects this research is expected to lead to significant improvements in scintillator performance. Scintillator materials convert various types of radiation into photons, which can then be collected and analyzed. Two important application areas are medical diagnostics, and gamma and neutron radiation detection. The relationship between crystalline defects and scintillator performance is an important topic and at the present time not well understood. The results of these studies will help to understand how to improve scintillator efficiency by leading to the design of improved scintillator compositions and structure. The research will enhance understanding of defect formation in ionic crystals and selection of improved methods of synthesis/processing for superior optical properties. The project will integrate research and education of undergraduate and graduate student participants. Training will be in a multi-disciplinary environment of basic and applied physics, materials science, electronics and photonics. In addition to providing support and mentoring of graduate students, the PIs will motivate undergraduate and high school students through a web site and make presentations to students on and off campus. The PIs will create a diverse research group that includes women and minority group members. Research results will be disseminated through publications in premier journals and via presentations at conferences and in seminars.