[in Japanese]

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[in Japanese]

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  We report the fabrication and spectroscopy of graphene and its intercalation materials. We prepared single- and multi-layer graphene with or without a buffer layer on a SiC(0001) crystal by the hydrogen termination method. We also prepared Li- or Ca-intercalated bilayer graphene by the atom-replacement method. By using ARPES (angle-resolved photoemission spectroscopy), we studied the electronic structure of this novel graphene family. We observed a clear difference in the electronic structure between graphene with and without a buffer layer, which accounts for the reported difference in the transport properties between the two. In intercalated bi-layer graphene, we found an interlayer band below the Fermi level in the Ca case while it is absent in the Li one. This suggests a possible two-dimensional superconductivity in the thinnest limit of graphite intercalation compounds.

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  Silicene is a two dimensional material of silicon and has zero-gap semiconductor characteristics as is garaphene, where nnergy dispersion reveals Dirac-Fermion nature.
  Moreover, silicene is expected to be very sensitive to electric field due to its buckled structure. In this paper, we discuss the Dirac-Fermion nature of silicene and propose a recipe for synthesis for free-standing silicene by the theoretical approaches.

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  With great success of graphene, a novel two-dimensional honeycomb lattice has been explored. Silicene, a honeycomb lattice of silicon atoms, is a candidate as an innovative material as it can acquire not only the Dirac fermion characters but exotic properties of the topological insulator. Recently, silicene has been synthesized on the Ag(111) surfaces. We review the state-of-the-art, including our recent achievements, of silicene grown on Ag(111). By using scanning tunneling microscopy/spectroscopy (STM/STS), low-energy electron diffraction (LEED), and density functional theory (DFT) calculations, we have revealed the geometric and electronic structures of the single layer silicene. We have found that the interaction between the silicene and the underlying Ag substrate is strong, and thus silicene on Ag surfaces loses the Dirac fermion character.

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  Ion conductive polymer is one of the key materials of solid state electrolytes used in various devices such as sensors and actuators of Micro Electro Mechanical Systems (MEMS). Especially, Nafion^®(DuPont) is the most important ion conductive polymer material and is used as Ionic Polymer-Metal Composite (IPMC) actuator. We have developed a novel dry plasma process for the fabrication of electrodes onto Nafion surfaces in our previous study. In this study, we fabricated IPMC actuators with Au, PtPd or Ag electrodes by our method. We found the maximum displacement (9 μm) was observed with the actuator of Au/electrode when the triangular wave (4 V, 200 mHz) was applied. The maximum displacement per unit charge was also observed with the actuator of Au electrode.

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