Understanding of optical luminescence mechanism of phosphors by establishment of X-ray luminescence holography

x射线激发光学发光（XEOL）已被应用于选择性位置的XAFS测量。另一方面，原子分辨率x射线全息术可以确定特定原子周围的局部结构，通常使用x射线荧光。在开始这个项目之前，一直没有使用XEOL的其他x射线全息摄影的想法。为了探索XEOL应用的新的分析可能性，我们重点研究了x射线入射光束角度各向异性的XEOL强度，并研究了原子分辨率x射线全息术的可行性。在Al_2O_3（蓝宝石）单晶上采用ZnO外延膜，因为已知ZnO和蓝宝石会发生XEOL。实验是在同步辐射设备SPring-8上进行的。观察到的XEOL的强度变化符合Al_2O_3衬底的全息图，与Zn Kα的x射线荧光全息图不同。为了更准确地描述XEOL全息图，我们通过对给定方向的互反晶格空间进行平均，估计了在全息图模式中观察到的x -鼠驻波线的位置和振幅。ZnO/Al_2O_3的XEOL光谱测量表明，蓝宝石的发光占主导地位，这与XEOL全息图的结果一致。由于Al或Si等轻元素的内壳电离和被空气吸收的低截面，使用x射线荧光进行x射线全息测量通常是困难的。本研究表明，使用XEOL可以方便地进行光元件的硬x射线全息测量。此外，我们发现ZnO/AL_2O_3样品在冷却到100 K时，可以发出与ZnO薄膜弹隙对应的强紫外发光（373 nm）。利用光栅单色仪选择ZnO薄膜的发光，可以记录ZnO薄膜的全息图。少

X-ray excited optical luminescence (XEOL) has been applied to the site selective XAFS measurements. On the other hand, atomic resolution x-ray holography, which can determine local structure around a specified atom, normally uses the x-ray fluorescence. Before starting this project, there has been no idea of the use of XEOL for othe X-ray holography. To explore new analytical possibility of the XEOL application, we focused on X-ray incident beam angular anisotropy of the XEOL intensity and studied a feasibility of atomic resolution X-ray holography. A ZnO epitaxial film on Al_2O_3 (sapphire) single crystal was adopted for the sample in the present study, because the XEOL is known to be occurred for ZnO and sapphire. The experiments were done at the synchrotron radiation facility SPring-8. The observed intensity variation of the XEOL corresponded to the hologram pattern of Al_2O_3 substrate, which was different from the X-ray fluorescence hologram pattern of Zn Kα. In order to attribute … More the XEOL hologram, we estimated positions and amplitudes of the X-rat standing wave lines observed in the hologram patterns by averaging over a given direction of reciprocal lattice space. Measurement of the XEOL spectrum from the ZnO/Al_2O_3 showed that the luminescence from sapphire was dominant, and this was consistent with the result of the XEOL hologram. The X-ray holography measurement using x-ray fluorescence is generally difficult for light elements, such as Al or Si, because of its low cross section for inner shell ionization and the absorption by air. The present study demonstrates that hard x-ray holography measurement for light element can be easily carried out using XEOL. Moreover, we found that the ZnO/AL_2O_3 sample used here emit the strong ultraviolet luminescence (373 nm), which corresponded to bang gap of ZnO thin film, by cooling to 100 K. By selecting the luminescence from ZnO thin film using a grating monochromator, the hologram pattern of ZnO layer could be recorded. Less