NaI晶体中Eu掺杂缺陷化学的原子分辨力显微镜研究
Defect chemistry of Eu dopants in NaI scintillators studied by atomically resolved force microscopy
摘要：
激活剂杂质及其在基质晶格中的分布在闪烁现象中起着关键作用。在这里，结合横截面非接触原子力显微镜（nc-AFM），X射线光电子能谱学（XPS）和密度泛函理论（DFT）被用来研究Eu 2+掺杂剂的分布在NaI闪烁体激活的3%的EuI 2。两种类型的沉淀结构被发现：第一，针状EuI 2沉淀与层状结构可能是负责散射的闪烁光。在具有良好闪烁性能的透明晶体中，发现了具有立方晶体结构且尺寸小于4 nm的沉淀物。在所有研究样品中检测到令人惊讶的低浓度点缺陷。在退火时，Eu向表面偏析，这导致形成具有EuI 2组合物和明显的单向莫尔图案的有序六方覆盖层。
英文摘要：
Activator impurities and their distribution in the host lattice play a key role in scintillation phenomena. Here a combination of cross-sectional noncontact atomic force microscopy (nc-AFM), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) was used to study the distribution of Eu2+ dopants in a NaI scintillator activated by 3% of EuI2. Two types of precipitate structures were found. First, needle-shaped EuI2 precipitates with a layered structure are likely responsible for scattering the scintillation light. In transparent crystals with good scintillation properties, precipitates with a cubic crystal structure and a size below 4 nm were found. A surprisingly low concentration of point defects was detected in all of the investigated samples. Upon annealing, Eu segregates towards the surface, which results in the formation of an ordered hexagonal overlayer with the EuI2 composition and a pronounced, unidirectional moire pattern.
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