Surface Analysis by Using Inverse Photoelectron Spectroscopy

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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.