Development of a surface analysis method by X-ray traveling waves using an X-ray wave guide

我们在目前的研究中发现，测量多层膜样品的白X射线反射率是表征多层膜的有力工具(正在申请专利)，并且X射线反射率对于X射线波导现象表现出伪对称图案。这种表面分析方法是基于这样的物理现象，即高于临界能量的X射线会被反射，而低于临界能量的X射线会在界面上折射。类似的表面分析方法也存在，但它们存在X射线探测器饱和的问题，因为入射的强X射线直接照射在探测器窗口上。在本研究中，我们避免了饱和，因此本方法作为一种表面分析方法在实际应用中是非常有效的。我们开发了一个用于分析实验数据的计算机程序，该程序的源代码已经在网页上公开，可以免费下载。在非等角反射下测量X射线反射率时，能谱有向低能侧移动的趋势，这在理论上已经得到了成功的再现。因此，可以通过测量入射角度变化的能谱来表征表面。我们还用电池制作了便携式X射线分析仪，并成功地分析了分析物表面的ppm级元素。伪对称图案之所以能观察到是一个悬而未决的问题；伪对称图案类似于所谓的Yoneda机翼，这与表面粗糙度密切相关。因此，伪对称图案可以具有关于表面粗糙度的信息。综上所述，我们通过比较X射线反射率的测量和理论计算，发展了一种利用表面行波引导通过表面和界面的表面分析方法。

We have found in the present research that the measurement of the white X-ray reflectivity for multilayer samples is a powerful tool to characterize multilayers (under patent application), and that the X-ray reflectivity exhibits pseudo-symmetric pattern for X-ray wave guide phenomena. This surface analysis method is based on the physical phenomena that X-rays higher energy than the critical energy will reflect, while X-rays lower energy than the critical energy will refract at the interface. Similar surface analysis methods exist but they have a problem of the saturation of the X-ray detector Because the incident direct strong X-rays impinge on the detector window. In the present research, we have avoided the saturation and consequently the present method is highly effective for the practical use as a surface analysis method. We have developed a computer program to analyze the experimental data, and the source code of it has been open in the Web page, and it can be freely downloaded. When the X-ray reflectivity is measured at the off-equiangular reflection, the energy spectrum tends to shift to the lower energy side, which has been successfully reproduced theoretically. Therefore the surface can be characterized by the measurement of an energy spectrum with the change of the angle of incidence. We have also made a portable X-ray analyzer using an electric battery, and succeeded to analyze ppm level elements on the analyte surface. The reason why the pseudo-symmetric pattern is observable is an open problem ; the pseudo-symmetric pattern resembles the so-called Yoneda wing, which is closely related to the surface roughness. Therefore the pseudo-symmetric pattern may have an information on the surface roughness. In summary, we have developed a surface analysis method by comparing the measurement of X-ray reflectivity and theoretical calculation, using surface traveling X-ray waves guided through the surface and interfaces.