Publications (6)1.01 Total impact
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Article: Electronic structure of pristine and K-doped solid picene: Non-rigid-band change and its implication for electron-intramolecular-vibration interaction
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ABSTRACT: We use photoemission spectroscopy to study electronic structures of pristine and K-doped solid picene. The valence band spectrum of pristine picene consists of three main features with no state at the Fermi level (EF), while that of K-doped picene has three structures similar to those of pristine picene with new states near EF, consistent with the semiconductor-metal transition. The K-induced change cannot be explained with a simple rigid-band model of pristine picene, but can be interpreted by molecular orbital calculations considering electron-intramolecular-vibration interaction. Excellent agreement of the K-doped spectrum with the calculations points to importance of electron-intramolecular-vibration interaction in K-doped picene. Comment: This article is accepted by Physical Review B11/2010; -
Article: Near E-F electronic structure of heavily boron-doped superconducting diamond
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ABSTRACT: We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES) of a heavily boron-doped superconducting diamond film (T-c = 7.2 K) in order to Study the electronic structure near the Fermi level (E-F). Careful determination of measured momentum space that across F point in the Brillouin zone (BZ) and increase of an energy resolution provide further spectroscopic evidence that EF is located at the highly dispersive diamond-like bands, indicating that holes at the top of the diamond-like valence band play an essential role for the conducting properties of the heavily boron-doped superconducting diamond for this boron-doping region (effective carrier concentration of 1.6%). The SXARPES intensities at E-F were also mapped out over BZ to obtain experimental Fermi surface sheets and compared with calculations. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.Journal of Physics and Chemistry of Solids. 01/2008; 69:2978-2981. -
Article: Core-level electronic structure evolution of heavily boron-doped superconducting diamond studied with hard x-ray photoemission spectroscopy
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ABSTRACT: Hard x-ray photoemission spectroscopy has been used to study intrinsic core-level electronic structure evolution of heavily boron-doped superconducting diamond films made with a microwave plasma-assisted chemical-vapor deposition method. The boron concentration dependent C 1s core-level spectra show system-atic changes in the shift of the main peak and in the evolution of an additional feature at 1.1– 1.3 eV lower binding energy than the main peak. In comparison to a low boron concentration nonsuperconducting diamond, the higher boron concentration doped diamond films show formation of several additional features in the B 1s core levels. Based on the present results, the local chemical environments around the doped boron atoms, the efficiency of hole doping by boron doping, and the implications for a recent x-ray absorption study are discussed.PHYSICAL REVIEW B 75, 205117. 01/2007; -
Article: The electronic structure of Ca-intercalated superconducting graphite CaC6
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ABSTRACT: We have measured Ca-intercalated graphite superconductor CaC6 (Tc = 11.2 K) by soft X-ray photoemission spectroscopy in order to understand the electronic structure. For the valence band, we observed several structures that correspond to those of calculated density of states with the partial density of states of Ca 3d at the Fermi level (EF). We also observed core level spectra that are a very large asymmetric Ca 2p and asymmetric C 1s for CaC6, suggesting the existence of conduction electrons derived from Ca 3d and a charge transfer from Ca to graphene layer. These results provide spectroscopic evidence for PDOS of Ca 3d at EF. From a comparison of electronic structure of CaC6 and other graphite intercalation compounds (GICs), we found the difference between CaC6 and other superconducting GICs, which provides deeper understanding of the superconductivity of CaC6.Physica C Superconductivity 469:1041-1044. · 1.01 Impact Factor -
Article: Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC_ {6}
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ABSTRACT: We have performed soft x-ray photoemission studies of Ca-intercalated graphite superconductor CaC6(Tc=11.2 K). The valence-band spectrum shows six main structures, with a peak at the Fermi level (EF), which correspond to those of calculated DOS. The intensity of the EF peak is resonantly enhanced at the Ca 2p-3d threshold, providing spectroscopic evidence for the existence of Ca 3d electrons at EF, which is confirmed experimentally for the first time. The Ca 2p core-level spectrum has a very large asymmetric line shape, which is further possible suggestion of the existence of Ca 3d derived conduction electrons at Ca sites. These results strongly support the picture where Ca 3d derived interlayer band plays a crucial role for the superconductivity of this material with relatively high Tc.Phys. Rev. B. 80(3). -
Article: Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films
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ABSTRACT: We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES) of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ∼23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF) exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.Science and Technology of Advanced Materials.
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Institutions
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2007–2010
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Okayama University
Okayama-shi, Okayama-ken, Japan
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