Development of Small-Sized Scanning Tunneling Microscope with Auger-Electron Analyzer

本研究开发了一种新型的小型表面分析仪，它具有俄歇元素分析和扫描隧道显微镜（STM）两种重要的表面分析和观察功能。为了生产这样的分析仪，我们已经提出了一个特殊的STM尖端工作作为一个电子源的核心电子在表面上的激发，与从表面发射的俄歇电子的能量分析仪，在STM设备的基础上。实际上，我们已经设计并制作了这样一个系统。对于特殊尖端，我们成功地制备了具有屏蔽功能的尖端（以及Wehnelt函数），其可以消除由尖端偏压形成的强电场的影响（通常的问题），在使用用于电子轨道分析、聚焦离子束设备等的软件程序重复计算和尖端试验之后。对于电子能量分析器，采用柱面镜类型是因为其在信噪比方面的优势而不是延迟栅格类型。使用位于特殊尖端后面的柱面镜分析器，我们证实了可以在准确的动能下检测到来自样品表面的俄歇电子。此外，我们还证实了STM本身的原子分辨率。此外，通过计算，我们发现了通过在针尖周围增加透镜电极来提高俄歇电子能谱的空间分辨率。在此基础上，我们成功地研制出了“小型扫描隧道显微镜-俄歇电子分析仪”的原型系统。

In this research we have developed a new-type small-sized surface analyzer which includes two important and indispensable functions for surface analysis and observation : Auger element analysis and scanning tunneling microscopy (STM). To produce such an analyzer, we have proposed a special STM tip working as an electron source for the excitation of core electrons at the surface, with an energy analyzer for Auger electrons emitted from the surface, on the basis of an STM equipment. Actually we have designed and produced such a system. For the special tip, we have succeeded to prepare the tip with the shield function (and also the Wehnelt function) which can eliminate the effect of the strong electric field formed by the tip bias-voltage (the usual problem), after the repetition of calculations and tip-trials using software programs for the electron orbital analysis, the focused ion beam facility, and so on. For the electron energy analyzer, the cylindrical-mirror type was adopted because of the advantage in the signal-to-noise ratio rather than the retardation-grid type. Using the cylindrical-mirror analyzer located behind the special tip we confirmed that Auger electrons from sample surfaces can be detected at the accurate kinetic energies. Moreover, we also confirmed the atomic resolution of the STM itself. Furthermore, we found the progress of the spatial resolution for the Auger electron spectroscopy by the addition of the lens electrode around the tip using the calculation. From these results, we have succeeded to develop a prototype system of "the small-sized scanning tunneling microscope with Auger-electron analyzer".