Development of STM combined with synchrotron-radiation light source and its application to elemental analysis and spin observation

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We have developed an ultrahigh vacuum (UHV) STM system with which we can take atomically resolved STM images under an Iiradiation of synchrotron radiation light source. In order to do that, we designed an anti-vibration system including a vibration-isolation table which can be fitted in a narrow space of beamline. Since sites of beamlines in synchrotron-radiation light source are usually quite noisy electrically and mechanically, which is completely inappropriate for STM, we needed to consider carefully to avoid the noises to disturb the operation of STM, and successfully took atomically resolved STM images of the Si(111)7x7 surface under the irradiation.We also succeeded in taking adsorption spectra of the sample element by using the probe tip as a detector; it was found that the photoinduced current increases when the irradiated light energy is above 101eV, an adsorption edge of Si 2p, demonstrating a possibility that the STM tip can detect photoelectron emitted from core states of sample. Compared with the previous work done with a X-ray tube, the photoinduced current by the synchrotron is larger by a factor of more than 100. High intensity of the light and tunability of a light energy to that of a high adsorption crosssection are the main reasons for the high detection.After an modificatIon of the measurement system, we could also measure the photoinduced current quantitatively. From the quantitative measurement we characterized a spatial resolution of this elemental detection method by using a sample with a mixture of Au-induced 5x2 and Si7x7 surfaces and a Si substrate on which 2-micron size aluminum dots are regularly arranged. We also developed a method to focus the detection area on the tip for improving the spatial resolution by coating the tip with an insulating polymer and found successfully working.