Surface Analysis by Using Inverse Photoelectron Spectroscopy

光电子能谱是观察许多物质中占据电子态的一种众所周知的方法。近年来，逆光电光谱学引起了人们的广泛关注，因为我们可以利用它来研究未占据的电子态。然而，应用逆光电子能谱法还存在许多技术问题。我们的目标是建立逆光电子能谱仪，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未占据电子态。然而，在实现目标的过程中，我们发现在逆光电子能谱实验中，表面电子态发生了巨大的变化。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，我们集中精力研究电子束诱导的表面反应。我们发现，电子轰击在NaCi和KCI晶体的表层产生氰化物离子。从温度依赖性的实验结果讨论了其产生机理。还观察了组成原子和离子的溅射，并对其机理进行了讨论。此外，在高温超导体中还观察到电子束诱导的分子发光现象，并将其归因于表面氰化物离子。

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.