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

技术支持：本计画的目的在于更深入了解掺稀土钇铝石榴石（YAG）闪烁体晶体中激子与晶体缺陷间的相互作用。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。YAG结构中的晶格缺陷将通过对其类型、尺寸和浓度的全面研究，使用正电子寿命谱进行表征。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。正电子参数和光学性质之间的相关性将被监测作为生长条件的函数，稀土掺杂剂的选择，掺杂水平，偏离化学计量和postgrowth治疗。相关性将进一步检查以下处理步骤，包括在不同气氛下的热退火。表征的结果将被用来修改合成和生长条件，以改善光学性能。非技术性：该项目涉及材料科学专题领域的基础研究问题，与电子和光子学技术相关。通过更好地理解激子与缺陷的相互作用，这项研究有望导致闪烁体性能的显着改善。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探测。晶体缺陷和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效率。该研究将增强对离子晶体中缺陷形成的理解，并选择改进的合成/加工方法以获得上级光学性能。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还将通过网站激励本科生和高中生，并向校内和校外的学生做演讲。PI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。研究成果将通过在主要期刊上发表文章以及在会议和研讨会上发表演讲的方式传播。

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.