Surface Analysis by Using Inverse Photoelectron Spectroscopy

光电子能谱是一种众所周知的方法，可以看到许多物质中的占据电子状态。近年来，逆光电能谱技术由于可以用来研究金属、半导体和绝缘体表面的空电子态而引起了人们的极大兴趣。然而，逆光电能谱技术的应用还存在着许多技术问题。我们的目标是建立逆光电能谱仪，特别是在软X射线能区，并研究金属、半导体和绝缘体表面的空电子态。在实现这一目标的过程中，然而，我们已经发现，表面电子态的变化剧烈的实验与逆光电子能谱。这种变化源于电子束引起的表面反应，电子束是进行逆光电子能谱实验的重要装置。因此，我们集中精力研究了电子束引起的表面反应，发现电子轰击NaCl和KCl晶体表面层产生了氰根离子。从它们的温度依赖性的实验结果讨论了产生机制。还观察到了组分原子和离子的溅射，并对其机理进行了讨论。此外，在高温超导体中还观察到了电子束诱导的分子发光，这种发光归因于表面氰离子。

Photoelectron spectroscopy is a well-known method to see occupied electronic states in many substances. Recently, inverse photoelectroti spectroscopy attracts much interest, since we can investigate unoccupied electronic states by using it. however, there are lots of technical problems to apply the inverse photoelectron spectroscopy.We have aimed to construct inverse photoelectron spectrometer, especially in the soft-x-ray energy region and to investigate unoccupied electronic states of surfaces in metals, semiconductors, and insulators.On the way to our goal, however, we have found that surface electronic states change drastically in the experiment with inverse photoelectron spectroscopy. This change originates from the surface reaction induced by electron beam, which is an important device to conduct an experiment of inverse photoelectron spectroscopy. Thus, we have focused our power to investigate the surface reaction induced by electron beam.We have found that cyanide ions are produced in the surface layers of NaCi and KCI crystals by electron bombardment. The production mechanisms were discussed from experimental results of their temperature dependence. The sputtering of constituent atoms and ions was also observed, and its mechanisms were discussed. Moreover, the molecular luminescence Induced by electron beam was observed in high temperature superconductors and it was attributed to the surface cyanide ions.