Faculty Profiles - YOKOYA Takayoshi

Papers - YOKOYA Takayoshi

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Angle-resolved photoemission spectroscopy for VO2 thin films grown on TiO2 (001) substrates Reviewed

Y. Muraoka, K. Saeki, Y. Yao, T. Wakita, M. Hirai, T. Yokoya, R. Eguchi, S. Shin

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 181 ( 2-3 ) 249 - 251 2010.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We present the results of angle-resolved photoemission spectroscopy (ARPES) measurements of metallic VO2 thin films. The VO2 thin films have been grown on TiO2 (0 0 1) single crystal substrates using pulsed laser deposition. The films exhibit a first-order metal-insulator transition (MIT) at 305K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive feature in the binding energy range of 3-8 eV along the Gamma-Z direction. The periodicity of the dispersive band is found to be 2.2 A(-1) which is almost identical with the periodicity expected from the c-axis length of the VO2 thin films. The overall feature of the experimental band structure is similar to the band structure calculations. supporting that we have succeeded in observing the dispersive band of the O 2p state in the metallic VO2 thin film. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO2. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2010.02.003

Bulk and surface physical properties of a CrO(2) thin film prepared from a Cr(8)O(21) precursor Reviewed

K. Iwai, Y. Muraoka, T. Wakita, M. Hirai, T. Yokoya, Y. Kato, T. Muro, Y. Tamenori

JOURNAL OF APPLIED PHYSICS 108 ( 4 ) 2010.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

We have prepared a CrO(2) thin film by chemical vapor deposition from a Cr(8)O(21) precursor and studied the bulk and surface physical properties. The CrO(2) thin film is grown on a TiO(2) (100) substrate by heating of a Cr(8)O(21) precursor and TiO(2) (100) substrate together in a sealed quartz tube. The prepared film is found from x-ray diffraction analysis to be an (100)-oriented single phase. The magnetization and resistivity measurements indicate that the film is a ferromagnetic metal with a Curie temperature of about 400 K. Cr 3s core-level and valence band photoelectron spectroscopy spectra reveal the presence of a metallic CrO(2) in the surface region of the film. Our work indicates that preparation from a Cr(8)O(21) precursor is promising for obtaining a CrO(2) thin film with the metallic surface. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3471811]

DOI： 10.1063/1.3471811

Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3-hexylthiophene) Thin Film Reviewed

Kaname Kanai, Takahiro Miyazaki, Takanori Wakita, Kouki Akaike, Takayoshi Yokoya, Yukio Ouchi, Kazuhiko Seki

ADVANCED FUNCTIONAL MATERIALS 20 ( 13 ) 2046 - 2052 2010.7

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

How annealing influences the morphology of a highly regioregular poly(3-hexylthiophene) (RR-P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high-molecular-weight (MW) RR-P3HT films tend to show low crystallinity even, after annealing, it is found that high-MW RR-P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR-P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high-MW RR-P3HT film.

DOI： 10.1002/adfm.201000116

Angle-resolved photoemission observation of the superconducting-gap minimum and its relation to the nesting vector in the phonon-mediated superconductor YNi2B2C Reviewed

T. Baba, T. Yokoya, S. Tsuda, T. Watanabe, M. Nohara, H. Takagi, T. Oguchi, S. Shin

PHYSICAL REVIEW B 81 ( 18 ) 2010.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We have performed ultrahigh-resolution angle-resolved photoemission spectroscopy to directly study the large superconducting (SC) gap anisotropy of YNi2B2C. We succeed in measuring momentum (k) dependence of SC gap for individual Fermi surface (FS) sheets, which demonstrates complexity of SC gap in a phonon-mediated superconductor. Within measured k regions on FS sheets, we find a pointlike minimum of SC gap, whose k positions can be connected by the known nesting vector. This shows close correlation between the nesting vector and node formation.

DOI： 10.1103/PhysRevB.81.180509

Room temperature ferromagnetic behavior in the hollandite-type titanium oxide Reviewed

K. Noami, Y. Muraoka, T. Wakita, M. Hirai, Y. Kato, T. Muro, Y. Tamenori, T. Yokoya

JOURNAL OF APPLIED PHYSICS 107 ( 7 ) 2010.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

A hollandite-type K(x)Ti(8)O(16) polycrystalline sample has been prepared and studied by magnetization, resistivity and x-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behavior is observed in the magnetic hysteresis measurement. The sample shows a semiconductive temperature dependence in the resistivity measurement. Analysis of the Ti 2p(3/2) core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti(4+) and Ti(3+). In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti(3+) ions in the hollandite-type TiO(2) lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type K(x)Ti(8)O(16) sample can be classified as a TiO(2)-based wide-gap semiconductor with Curie temperature above room temperature. Room temperature ferromagnetism (RTFM) decreases in the sample prepared under a strong reducing gas atmosphere, accompanied with the decrease in the resistivity. The results imply that the localized 3d electrons are responsible for the RTFM of the K(x)Ti(8)O(16) sample. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3369500]

DOI： 10.1063/1.3369500

Kondo scaling of the pseudogap in CeOs4Sb12 and CeFe4P12 Reviewed

P. A. Rayjada, A. Chainani, M. Matsunami, M. Taguchi, S. Tsuda, T. Yokoya, S. Shin, H. Sugawara, H. Sato

JOURNAL OF PHYSICS-CONDENSED MATTER 22 ( 9 ) 2010.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

CeOs4Sb12 and CeFe4P12 are classified as Kondo semiconductors, which show coupled changes in electrical transport, thermodynamic and magnetic properties with a low-temperature semiconductor-like electrical resistivity. We have carried out core level and valence band photoemission spectroscopy on single crystal CeOs4Sb12 and CeFe4P12 to study their electronic structure and the evolution of states at the Fermi level as a function of temperature (similar to 10-300 K). The Ce 3d core level spectra show the presence of f(0), f(1) and f(2) final states with very different relative intensities in the two compounds. Single-impurity Anderson model calculations provide f electron counts of n(f) = 0.97 and 0.86 per Ce atom, suggestive of a low-and high-T-K (=single ion Kondo temperature) for CeOs4Sb12 and CeFe4P12, respectively. The high-resolution temperature-dependent near-Fermi level spectra show pseudogaps of energy similar to 50 meV and similar to 110 meV in the valence band density of states (DOS) of CeOs4Sb12 and CeFe4P12, respectively. The temperature dependence of the DOS at the Fermi level follows the change in effective magnetic moment estimated from magnetic susceptibility for both materials, confirming the Kondo nature of the pseudogap in CeOs4Sb12 and CeFe4P12. A compilation of measured pseudogaps using photoemission and optical spectroscopy identifies the charge gaps Delta(C) for Ce-based Kondo semiconductors and provides a direct relation with T-K given by Delta(C) similar to 2k(B)T(K). In conjunction with the known behaviour of the spin gaps Delta(S) similar to k(B)T(K), the results establish the coupled energy scaling of the spin and charge gaps in Kondo semiconductors.

DOI： 10.1088/0953-8984/22/9/095502

Low voltage operation in picene thin film field-effect transistor and its physical characteristics Reviewed

Yumiko Kaji, Naoko Kawasaki, Xuesong Lee, Hideki Okamoto, Yasuyuki Sugawara, Shohei Oikawa, Akio Ito, Hiroyuki Okazaki, Takayoshi Yokoya, Akihiko Fujiwara, Yoshihiro Kubozono

APPLIED PHYSICS LETTERS 95 ( 18 ) 2009.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Low voltage operation of picene thin film field-effect transistor (FET) has been realized with 40 nm thick SiO(2) gate dielectrics coated by two polymers, Cytop (TM) and polystyrene. The picene FETs operated in low absolute gate voltage vertical bar V(G)vertical bar below 15 V for Cytop (TM) coated SiO(2) and 30 V for polystyrene coated SiO(2) gate dielectrics, and they showed a significant O(2) gas sensing effect down to similar to 10 ppm. Photoemission spectrum clarified that O(2) molecules penetrate into the thin films at O(2)/picene mole ratio of 1: 1. X-ray diffraction pattern of picene thin films showed highly oriented growth on the polymer-coated SiO(2).

DOI： 10.1063/1.3257373

Study of electronic states for V thin films deposited on 6H-SiC substrates by soft X-ray emission spectroscopy Reviewed

M. Hirai, H. Okazaki, R. Yoshida, M. Tajima, K. Saeki, Y. Muraoka, T. Yokoya

APPLIED SURFACE SCIENCE 256 ( 4 ) 948 - 949 2009.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Silicon carbide (SiC) is a candidate material for electronic devices to operate upon crucial environment. Electronic states of silicides and/or carbide/graphite formed in metal/SiC contact system is fundamentally important from the view point of device performance.
We study interface electronic structure of vanadium (V) thin-film deposited on 6H-SiC(0 0 0 1) Si-face by using a soft X-ray emission spectroscopy (SXES). For specimens of V(38 nm)/6H-SiC (substrate) contact systems annealed at 850 degrees C, the Si L(2,3) emission spectra indicate different shapes and peak energies from the substrate. The product of materials such as silicides and/or ternary materials is suggested. Similarly, the C K alpha emission spectra show the shape and peak energy characteristic of vanadium carbide including substrate 6H-SiC signal. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2009.05.120

Band dispersion near the Fermi level for VO2 thin films grown on TiO2 (001) substrates Reviewed

K. Saeki, T. Wakita, Y. Muraoka, M. Hirai, T. Yokoya, R. Eguchi, S. Shin

PHYSICAL REVIEW B 80 ( 12 ) 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We have performed angle-resolved photoemission spectroscopy (ARPES) measurements of VO2 using epitaxial thin films and observed the band dispersion near the Fermi level (E-F) for this compound. The VO2 thin films have been grown on TiO2 (001) single-crystal substrates using pulsed laser deposition. The films exhibit a first-order metal-insulator transition (MIT) at 305 K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive features in the binding-energy range of 3-8 eV along the Gamma-Z direction. Also, the V 3d state shows two dispersive bands around the Gamma point near E-F, indicative of two electron pockets centered at the Gamma point. Both electron pockets have an occupied bandwidth of about 0.4 eV. Assuming the parabolic energy bands around the Gamma point, the effective-mass ratios of the two electron pockets are estimated to be about 0.2 and 1. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO2 and thus would play a crucial role to elucidate the mechanism of the MIT in VO2.

DOI： 10.1103/PhysRevB.80.125406

The electronic structure of Ca-intercalated superconducting graphite CaC6 Reviewed

H. Okazaki, R. Yoshida, K. Iwai, K. Noami, T. Muro, T. Nakamura, T. Wakita, Y. Muraoka, M. Hirai, F. Tomioka, Y. Takano, A. Takenaka, M. Toyoda, T. Oguchi, T. Yokoya

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 469 ( 15-20 ) 1041 - 1044 2009.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We have measured Ca-intercalated graphite superconductor CaC6 (T-c = 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 (E-F). 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 E-F. 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. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.05.172

Effect of antiferromagnetic ordering on temperature dependent superconducting gap in ErNi2B2C: Laser-photoemission spectroscopy Reviewed

T. Baba, T. Yokoya, S. Tsuda, T. Kiss, T. Shimojima, K. Ishizaka, H. Takeya, K. Hirata, N. Nakai, K. Machida, T. Togashi, C. T. Chen, C. Q. Zhang, S. Watanabe, S. Shin

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 469 ( 15-20 ) 928 - 931 2009.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We have performed temperature (T)-dependent laser-photoemission spectroscopy of antiferromagnetic (AF) superconductor ErNi2B2C to study the electronic structure, especially the effect of AF ordering in T-dependent superconducting (SC) gap. To estimate the values of T-dependent SC gap, we fitted the experimental data by Dynes function having an anisotropic s-wave SC gap. From the fitting results we, find a sudden deviation from the BCS prediction just below T-N. This observation can be well explained by the theoretical model, indicating that the origin of anomalous T-dependence is competition between rapid evolution of AF molecular field and SC condensation energy. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.05.101

Bulk-sensitive spectroscopic studies on noncentrosymmetric superconducting system of Mg-Ir-B Reviewed

R. Yoshida, H. Okazaki, K. Iwai, K. Noami, T. Muro, M. Okawa, K. Ishizaka, S. Shin, Z. Li, J. L. Luo, G. -Q. Zheng, T. Oguchi, M. Hirai, Y. Muraoka, T. Yokoya

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 469 ( 15-20 ) 1034 - 1036 2009.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We present the data from ultrahigh-resolution laser-excited photoemission spectroscopy on a newly discovered noncentrosymmetric superconcluctor Mg(10)Ir(19)B(16). We observed the evidences for the opening of superconducting gap where numerical fittings show that isotropic s-wave model can satisfactorily explain the behavior of spectra near the Fermi level. We also present the valence band photoemission spectrum and B K fluorescence spectrum to discuss the basic electronic structure of Mg(10)Ir(19)B(16). (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2009.05.175

Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC6 Reviewed

Okazaki H, Yoshida R, Iwai K, Noami K, Muro T, Nakamura T, Wakita T, Muraoka Y, Hirai M, Tomioka F, Takano Y, Takenaka A, Toyoda M, Oguchi T, Yokoya T

PHYSICAL REVIEW B 80 ( 3 ) 2009.7

Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC6 Reviewed

H. Okazaki, R. Yoshida, K. Iwai, K. Noami, T. Muro, T. Nakamura, T. Wakita, Y. Muraoka, M. Hirai, F. Tomioka, Y. Takano, A. Takenaka, M. Toyoda, T. Oguchi, T. Yokoya

PHYSICAL REVIEW B 80 ( 3 ) 2009.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We have performed soft x-ray photoemission studies of Ca-intercalated graphite superconductor CaC6 (T-c=11.2 K). The valence-band spectrum shows six main structures, with a peak at the Fermi level (E-F), which correspond to those of calculated DOS. The intensity of the E-F peak is resonantly enhanced at the Ca 2p-3d threshold, providing spectroscopic evidence for the existence of Ca 3d electrons at E-F, 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 T-c.

DOI： 10.1103/PhysRevB.80.035420

Ishizaka et al. Reply Reviewed

K. Ishizaka, R. Eguchi, S. Tsuda, A. Chainani, T. Yokoya, T. Kiss, T. Shimojima, T. Togashi, S. Watanabe, C. -T. Chen, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi, H. Kawarada, S. Shin

PHYSICAL REVIEW LETTERS 102 ( 19 ) 2009.5

In situ positioning of a few hundred micrometer-sized cleaved surfaces for soft-x-ray angle-resolved photoemission spectroscopy by use of an optical microscope Reviewed

Takayuki Muro, Yukako Kato, Tomohiro Matsushita, Toyohiko Kinoshita, Yoshio Watanabe, Akira Sekiyama, Hiroshi Sugiyama, Masato Kimura, Satoshi Komori, Shigemasa Suga, Hiroyuki Okazaki, Takayoshi Yokoya

REVIEW OF SCIENTIFIC INSTRUMENTS 80 ( 5 ) 2009.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

A method to position samples with small cleaved regions has been developed to be applied to the angle-resolved photoemission spectroscopy (ARPES) which uses soft-x-ray synchrotron radiation focused down to 160x180 mu m(2). A long-working-distance optical microscope is used for the sample observation. A selected region on a sample can be optimally set at the position of measurements, which is realized by the spatial resolution of the photoelectron analyzer. Using this method, electronic band dispersions of bulk silicon have been measured by ARPES for a partially cleaved region with a size of similar to 200x500 mu m(2).

DOI： 10.1063/1.3124145

Electronic Structure of Superconducting FeSe Studied by High-Resolution Photoemission Spectroscopy Reviewed

Rikiya Yoshida, Takanori Wakita, Hiroyuki Okazaki, Yoshikazu Mizuguchi, Shunsuke Tsuda, Yoshihiko Takano, Hiroyuki Takeya, Kazuto Hirata, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Hisatomo Harima, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 3 ) 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have pet-formed soft x-ray and Ultralligh-resolution laser-excited photoemission measurements on tetragonal FeSe, which was recently identified as a superconductor. Energy dependent study of valence band is compared to band Structure Calculations and yields a reasonable assignment of partial densities of states. However, the sharp peak near the Fermi level slightly deviates from the calculated energy position, giving rise to the necessity of self energy correction. We have also performed ultrahigh-resolution laser photoemission experiment on FeSe and observed the suppression of intensity around the Fermi level upon cooling.

DOI： 10.1143/JPSJ.78.034708

Superconducting Gap and Valence Band of Mg10Ir19B16 Studied by Laser and Synchrotron Photoemission Spectroscopy Reviewed

Rikiya Yoshida, Hiroyuki Okazaki, Keisuke Iwai, Kengo Noami, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Zheng Li, Jianlin Luo, Guo-qing Zheng, Tamio Oguchi, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 3 ) 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We report the results of first photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg10Ir19B16. We measured the valence band structure of Mg10Ir19B16 using soft X-ray photoemission technique and found that the first principal calculation explains our observation well. In the bulk-sensitive laser-excited photoemission study, we observed that the intensity at the Fermi level decreases as we lower the sample temperature, indicative of the opening of superconducting energy gap. Using Dynes' function, we performed fitting analysis on the spectra of superconducting state.

DOI： 10.1143/JPSJ.78.034705

Strong-Coupling Superconductivity in Noncentrosymmetric Superconductor Li2Pd3B by Sub-meV Photoemission Spectroscopy Reviewed

Shunsuke Tsuda, Takayoshi Yokoya, Takayuki Kiss, Takahiro Shimojima, Kyoko Ishizaka, Shik Shin, Tadashi Togashi, Shuntaro Watanabe, Chengqian Zhang, Chuangtian Chen, Izumi Hase, Hiroyuki Takeya, Kazuto Hirata, Kazumasa Togano

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 3 ) 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

Noncentrosymmetric superconductors Li2Pd3B and Li2Pt3B are studied by high-resolution photoemission spectroscopy. The valence band spectra of Li2Pd3B and Li2Pt3B are well explained by first principles band calculations. The sub-meV photoemission result shows that the size of the superconducting gap of Li2Pd3B is about 1.1 meV at 5.4 K with a reduced gap value (2 Delta(0)/k(B)T(c)) of about 4.5, which is greater than the Bardeen-Cooper-Schrieffer (BCS) value of 3.52. The obtained superconducting gap can be explained more clearly with an s-wave superconducting gap than with p- and d-wave superconducting gaps. This result indicates that Li2Pd3B is a conventional strong-coupling superconductor.

DOI： 10.1143/JPSJ.78.034711

Soft X-ray Core-Level Photoemission Study of Boron Sites in Heavily Boron-Doped Diamond Films Reviewed

Hiroyuki Okazaki, Rikiya Yoshida, Takayuki Muro, Takanori Wakita, Masaaki Hirai, Yuji Muraoka, Yoshihiko Takano, Shingo Iriyama, Hiroshi Kawarada, Tamio Oguchi, Takayoshi Yokoya

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 3 ) 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have performed high-resolution soft x-ray B 1s core-level photoemission spectroscopy of heavily boron-doped diamond films in order to study the chemical sites of doped-boron atoms and their relation to the superconducting transition temperature (T-c). We find that B 1s core-level spectra exhibit several fine structures and three bulk components can he resolved from photon energy dependent studies and spectral fittings. These results indicate existence of several chemical environments of doped-boron atoms. One of the bulk components having the lowest binding energy can be assigned to a signal from substitutionally doped-boron atoms. Comparisons of bulk components with T-c suggest spectroscopic evidence for the importance of substitutionally doped-boron atoms for effective carrier and superconductivity.

DOI： 10.1143/JPSJ.78.034703

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