Development of Total-Reflection Angle Soft X-ray Spectroscopy combined with RHEED

Ino是该项目的研究人员之一，他发现，通过观察反射高能电子衍射(RHEED)的图案，可以探测到从只有一层全反射角度的金属薄膜发出的X射线共振线。他将这种新的表面分析方法命名为RHEED-全反射角X射线光谱分析(RHEED-TRAXS)。RHEED-TRAXS是一种同时观察RHEED图案和分析表面化学计量比的有力手段。此外，通过改变电子的入射角和X射线的提取角来分析薄膜的深度分布也是一种有用的方法。这个项目的目的是开发软X射线区域的RHEED-TRAXS，即RHEED-全反射角软X射线能谱(RHEED-TRASXS)，以展示这种方法在表面化学分析中的有效性，并建议RHEED-TRASX的实际应用。在这台光谱仪中，使用了具有弯曲和变间距凹槽的像差校正凹面光栅来分割荧光X射线线。分离后的X射线由多通道平板检测，将X射线信号转换为可见光。真空室外的可见光通过观察口由一台CCD摄像机探测到。然而，在原型光谱仪系统上，信号太弱，无法检测到。因此，我们计划制作一台改进的光谱仪，将一台CCD相机放入真空中，直接用CCD相机检测X射线。2000年，我们购买了可用于真空放置的CCD相机。我们也是在我们的机械车间里使用真空中的CCD摄像机生产了改装后的光谱仪。改进后的频谱有了更好的S/N比。然而，韧致辐射与光谱重叠。攻克韧致辐射将使我们能够将RHEED-TRASXS投入实际应用。

Ino, one of the investigators on this project, discovered that an X-ray resonance line emitted from a metal thin film with only a layer, at the total-reflection angle, can be detected on observing the pattern of reflection high-energy electron diffraction (RHEED). He named the new surface analysis method "RHEED - Total-Reflection Angle X-ray Spectroscopy (RHEED-TRAXS)". The RHEED-TRAXS is a powerful method to observe RHEED pattern and to analyze the stoichiometry of the surface simultaneously. Moreover, it is a useful method to analyze the depth profile of thin films by changing the incident angle of the electron and the extraction angle of the X-ray. The purpose of this project is to develop the RHEED-TRAXS at the soft X-ray region, i.e., "RHEED - Total-Reflection Angle Soft X-ray Spectroscopy (RHEED-TRASXS)", to show the usefulness of this method for chemical analysis of surface, and to suggest the practical use of RHEED-TRASXS.In 1999, We produced a prototype soft X-ray spectrometer in our machine shop. In this spectrometer, aberration-corrected concave grating with curved and variable spacing grooves was used to split the fluorescent X-ray lines. The splitted X-rays were detected by a multi-channel plate to change the X-ray signal into the visible light. The visible light was detected by a CCD camera out of the vacuum chamber through a viewing port. On the prototype spectrometer system, however, the signal was to weak to detect. Therefore, we planned to make an improved spectrometer to put a CCD camera into the vacuum, detecting the X-rays by the CCD camera directly.In 2000, We bought the CCD camera available to put in vacuum. We produced the modified spectrometer, using the CCD camera in vacuum, also in our machine shop. The modification brought us better S/N ratios of the spectrum. However, bremsstrahlung was overlapped with the spectrum. To conquer the bremsstrahlung will enable us to put the RHEED-TRASXS to practical use.