光致光辐射探测材料陷阱分布及控制技术研究

As a new radiation detection technology, optically stimulated luminescence (OSL) has many advantages compared with the conventional thermoluminescence (TL). α-Al2O3:C single crystal is a good OSL material, but its shallow traps limit the measurement accuracy and application temperature range. How to control the shallow traps is critical to improve the OSL performance. In this proposal, the first-principles based on density functional theory (DFT) and VASP program will be used to study the electronic structure, trap energy level distribution, and luminescence of α-Al2O3:C and its doped and irradiated systems to understand the effects of various factors on the mechanism of trap formation. The theoretical protocol will be obtained to control the shallow traps of α-Al2O3:C systems, which will support the experimental investigations and parameter optimization. Based on the simulated results, the proper dopant elements will be selected and combined with the electron beam and γ-ray irradiations to prepare the modified α-Al2O3:C single crystals with different types of point defects and different trap distribution. The microstructure, trap distribution and (time-resolved) OSL will be characterized. The correlation between trap energy level distribution and OSL properties will be studied to obtain the control method of shallow traps and optimized doped crystal samples. The samples prepared with optimized parameters will be used for the dose detection experiments and the results will guide the confirmation and improvement of the control method of shallow traps. Finally, the protocol for shallow trap control in the α-Al2O3:C crystals will be obtained. This work is helpful for the applications of radiation detection materials.

作为一种新型辐射探测技术，光致光具有传统热释光技术无法比拟的优点，α-Al2O3:C晶体是一种良好的光致光材料，但浅陷阱的存在限制了测量精度和温度适用范围，如何控制浅陷阱成为提高其性能的关键。本项目拟利用基于密度泛函理论的第一性原理和VASP程序，研究α-Al2O3:C及掺杂和辐照后体系的电子结构、陷阱能级分布和发光性能，揭示各因素对陷阱形成机制的影响，得到浅陷阱缺陷控制的理论方案，为实验研究提供依据。参考理论结果，选择合适的掺杂元素并结合电子束、γ射线辐照制备改性的Al2O3:C晶体，引入不同类型点缺陷，改变陷阱能级分布，表征其微观结构、陷阱分布和（时间分辨）光致光特性。研究陷阱能级分布与发光特性之间的物理规律，获得浅陷阱控制方法和优化掺杂的晶体样品，并以此开展剂量监测实验，验证和改进浅陷阱控制方法，获得浅陷阱控制方法和工艺方案，为工程应用提供参考。

α-Al2O3:C晶体是一种良好的光致光材料，但浅陷阱的存在限制了测量精度和温度适用范围，如何控制浅陷阱成为提高其性能的关键。本项目采用了基于密度泛函理论的第一性原理和VASP程序，研究了中性C、B、P、S几种元素掺杂以及带电荷掺杂的α-Al2O3的态密度、电子结构、能带结构，C掺杂理想态和本征缺陷态（包括空位、间隙原子以及弗伦克尔对）α-Al2O3的空间几何结构、缺陷形成能和电子结构。采用了从头算分子动力学模拟研究了低能辐照条件下α-Al2O3的移位阈能、缺陷和分布情况。采用聚丙烯酰胺聚合凝胶法制备了不同含量C掺杂以及Zn、Ti、Fe、Ni金属元素与C共掺杂α-Al2O3材料，研究其微观结构和形貌以及发光特性。研究了He、Zn、Ti、Fe、Ni离子束辐照和电子束辐照对α-Al2O3:C晶体发光特性的影响。结果表明，C掺杂含量控制在1%以下，以及采用合适的金属元素，如Zn、Ti与C共掺杂能改善α-Al2O3的光致光特性。