A Study of Photoelectron Emission Patterns from the Super-Structures on Semiconductor Surfaces Using a New Electron Energy Analyzer

本研究的主题是利用一种新型的显示式球面反射镜分析仪研究半导体表面超结构的光电子发射图案。该分析仪可以显示样品表面发射的一个动能的带电粒子的角分布图样。这个分析器的特点是：(1)图案不失真；(2)接受锥最终宽(2pi立体)。在，用X射线或同步辐射(SR)测量了来自核心电子的光电子的角分布。所用样品晶体为Si、TaC、W等，吸附物为Ga原子。芯层光电子的角分布图样包含结构信息，因为它们从样品表面逸出时会受到衍射过程的影响。因此，对图案的分析给出了发射原子周围的结构。利用SR(参考文献)获得了许多新的模式。1990年用He-I或He-II共振灯测量了价带态光电子的角分布。这个能区的角分布图案显示了电子能带结构的二维图。因此，这一研究可以给出有关能带结构的精确信息，特别是费米面的形状。所使用的样品是单晶石墨(Kish石墨)。得到的能带结构与理论或文献中的实验结果符合得很好。这是日本第一次，也是世界上第二次对能带结构进行二维测量。

The subject of this research is the study of the photoelectron emission patterns from the superstructures on semiconductor surfaces using a new display-type spherical mirror analyzer. This analyzer can display the angular distribution pattern of charged particles of one kinetic energy emitted from a sample surface. The characteristics of this analyzer are (1) the pattern is not distorted, (2) the acceptance cone is ultimately wide (2pi steradian).In 1989 the angular distribution pattern of the photoelectrons from core electrons have been measured using X-rays or synchrotron radiations (SR). The sample crystals used were Si, TaC, W etc., and adsorbate was Ga atoms. The angular distribution pattern of core photoelectrons involve structural informations because they suffer from diffraction process when they escape from the sample surface. The analysis of the pattern thereby gives the structure around the emitting atom. Many new patterns have been obtained using SR (ref. 5, 6).In 1990 the angular distribution pattern of the photoelectrons from valence band states have been measured using He I or II resonance lamp. The angular distribution pattern at this energy region shows the 2-dimensional map of the electronic energy band structure. Hence, this study may give precise informations about the band structure especially the shape of the Fermi surface. The sample used was a single crystal of graphite (Kish graphite). The obtained band structure was in good agreement with theory or the experimental ones in the literatures. This result is the first 2-dimensional measurement of the band structure in Japan, and the second one in the world.