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Observation of lateral nano-structures at solid surface is of great importance to explore low-dimensional materials and create new micro-functional devices. Various microscopic methods have been developed to observe lateral morphological and elemental images at nanometer scale. However, it is difficult to identify valence states, which are essential parameters to determine the properties of micro-devices. Here we present the results for the chemical-state-selective mappings of micro-patterns for silicon compounds by means of photoelectron emission microscopy (PEEM) excited by soft X-rays from synchrotron light source. Sample surfaces were illuminated by synchrotron soft X-rays around the Si K-edge. Total photoelectrons emitted from the microscopic area were focused on the YAG screen using electrostatic lenses, and the images were detected by CCD camera. The samples investigated were micro-patterns of silicon oxides, silicon nitrides, and organic silicon compounds. The micro-patterns of silicon oxides were prepared by O2+ ion implantation in Si(001) using a mask at 7.5 mm periodicity. For the X-ray absorption spectra of Si (Si0), SiO (Si2+), and SiO2 (Si4+), the resonance peaks were observed at 1841.9 eV, 1844.6 eV and 1847.3, respectively, originating from the resonant excitations from the Si 1s to the unoccupied Si3p* states of the respective valence states. By scanning the X-ray energy, we succeeded in observing the sub-micron images depending on the valence states. Since the surface of this sample is morphologically flat, it is demonstrated that the present method can be applied to the observation on microscopic images depending only on the valence states of silicon. When we annealed the sample, the lateral diffusion was observed from 700°C. During the annealing, however, no intermediate valence states were observed at the Si-SiO2 interfaces. It was elucidated that the diffusion of oxygen induced the sudden changes of the Si valence states from Si0 to Si4+ without any intermediate valence states. The results for the chemical-state-selective mappings and lateral diffusions are also presented for silicon nitrides and organic silicon compounds.
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