Construction of the undulator beamline equipped with a UHV-STM for observations of synchrotron-radiation-stimulated surface reaction

An undulator beamline equipped with a UHV-scanning tunneling electron microscopy (STM) system has been designed and constructed at the UVSOR facility to investigate synchrotron-radiation-stimulated reactions. Using this undulator beamline, we have observed irradiation effects on the hydrogen terminated-(H-) Si(1 1 1) surfaces in atomic scale. The small protrusions, which are assigned to the rest-atom with missing H, appeared on the monohydride surface after irradiation. The density of them monotonically increased with irradiation dose. This phenomenon has been observed almost independent on the Si 2p core electron excitation threshold, indicating the significant contribution of the valence electron excitations to the Si H bond dissociations