Analysis of surface electronic structure by STM with resonance excitation

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(1)Development of apparatus for simultaneous measurements of STM. STS and STM light emission spectra.The experimental system of Scanning Probe Microscopy for STM, STS and STM light, emission measurements has been developed. The light emitted from STM is collected by using lens installed in STM head. These three kinds of measurements can be made simultaneously by communicating between STM controller and optical detecting system, which enables us the comparison among topographic image by STM, local density of states by STS and optical spectra by STM-induced light emission.(2)Comparison of light emission spectra with local density of states.We have measured STM-induced light emission from organic molecules adsorbed Au(111) surface at low temperatures of about 77K. The emission spectra have been measured at the same time of STS and STM measurements for octanedithiol films on Au(111) surfaces, and the optical spectra been correlated with topographic images by STM and local density of states by STS. These data have been compared with those for the clean Au(111) surface's.The change of optical spectra due to molecule adsorption has been observed in peak position and spectral shape in the longer wavelength side, of emission peak for' clean Au(111) surface : These change can be explained by the change in local density of states due to octanedithiol adsorption on Au (111) : the decrease in density of states at the energy near Fermi level and the increase above 0.3eV with respect to Fermi level. This comparison has been made successfully for the first time based on the simultaneous measurements by our experimental system