X-ray photoelectron spectroscopy (XPS) has been widely used for the surface analysis technique. The analysis depth (inelastic mean free path or photoelectron escape depth) is several nm, and it is possible to identify the elements existing on the sample surface, the apparent elemental composition, and the imaging of specific elements. It is also possible to estimate the surface layered structure by using some analysis methods. Due to these advantages, it is also used for the evaluation of organic materials such as polymers, monolayers and LB films. In some cases, however, accurate information cannot be obtained due to the decomposition of those materials by the irradiation of X-ray. Here, I will explain how to evaluate the decomposition characteristics of polymer materials and monomolecular films on solid surfaces, and how to determine sample damaging factors using reference substances.

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All-solid-state lithium batteries are expected to become the next generation of batteries. One of the major drawbacks for the practical use of all-solid-state batteries is their large interface resistance at the solid electrolyte and electrode interface. We have been investing electrolyte/electrode interfaces using all-solid-state thin-film batteries. In this study, we report an extremely low resistance of 8.6 Ωcm² at a solid electrolyte (Li₃PO₄) and electrode (LiCoO₂) interface. This value is an order of magnitude smaller than those presented in previous reports on all-solid-state batteries. Using synchrotron surface X-ray diffraction, we investigated the atomic structure of the Li₃PO₄/LiCoO₂ interfaces; the low-resistance interface exhibited a flat and well-ordered atomic arrangement at the electrode surface, whereas the high-resistance interface showed a disordered interface. These results indicate that the crystallinity of LiCoO₂ at the interface has a significant impact on interface resistance.

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X-ray Photoelectron Spectroscopy (XPS) is one of the tools for direct observation of surface chemical states. The environmental condition around sample need to be an ultra high vacuum condition in order to avoid discharge of analyzer and contamination on detector during conventional XPS measurements. Intensity drop due to interaction between photoelectron, X-ray and gaseous molecules makes it difficult to perform measurements in gaseous condition. Increase of request on measurement with gaseous condition promote development for new XPS technique recently. Frontier technique of XPS that enable to perform XPS at near ambient pressure condition and several results are revealed in this article.

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