Evaluation of doped potassium concentrations in stacked two-Layer graphene using real-time XPS

Ogawa, Shuichi*; Tsuda, Yasutaka; Sakamoto, Tetsuya*; Okigawa, Yuki*; Masuzawa, Tomoaki*; Yoshigoe, Akitaka; Abukawa, Tadashi*; Yamada, Takatoshi*

Applied Surface Science, 605, p.154748_1 - 154748_6, 2022/12

https://doi.org/10.1016/j.apsusc.2022.154748

Immersion of graphene in KOH solution improves its mobility on SiO/Si wafers. This is thought to be due to electron doping by modification with K atoms, but the K atom concentration C in the graphene has not been clarified yet. In this study, the C was determined by XPS analysis using high-brilliance synchrotron radiation. The time evolution of C was determined by real-time observation, and the C before irradiation of synchrotron radiation was estimated to be 0.94%. The C 1s spectrum shifted to the low binding energy side with the desorption of K atoms. This indicates that the electron doping concentration into graphene is decreasing, and it is experimentally confirmed that K atoms inject electrons into graphene.

Gas barrier properties of chemical vapor-deposited graphene to oxygen imparted with sub-electronvolt kinetic energy

Ogawa, Shuichi*; Yamaguchi, Hisato*; Holby, E. F.*; Yamada, Takatoshi*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Journal of Physical Chemistry Letters (Internet), 11(21), p.9159 - 9164, 2020/11

https://doi.org/10.1021/acs.jpclett.0c02112

Atomically thin layers of graphene have been proposed to protect surfaces through the direct blocking of corrosion reactants such as oxygen with low added weight. The long term efficacy of such an approach, however, is unclear due to the long-term desired protection of decades and the presence of defects in as-synthesized materials. Here, we demonstrate catalytic permeation of oxygen molecules through previously-described impermeable graphene by imparting sub-eV kinetic energy to molecules. These molecules represent a small fraction of a thermal distribution thus this exposure serves as an accelerated stress test for understanding decades-long exposures. The permeation rate of the energized molecules increased 2 orders of magnitude compared to their non-energized counterpart. Graphene maintained its relative impermeability to non-energized oxygen molecules even after the permeation of energized molecules indicating that the process is non-destructive and a fundamental property of the exposed material.

Detection of molecular oxygen adsorbate during room-temperature oxidation of Si(100)21 surface; In situ synchrotron radiation photoemission study

Yoshigoe, Akitaka; Yamada, Yoichi*; Taga, Ryo*; Ogawa, Shuichi*; Takakuwa, Yuji*

Japanese Journal of Applied Physics, 55(10), p.100307_1 - 100307_4, 2016/09

https://doi.org/10.7567/JJAP.55.100307

Synchrotron radiation photoelectron spectroscopy during the oxidation of the Si(100)21 surface at room temperature revealed the existence of the molecularly adsorbed oxygen, which was considered to be absent. The O 1s spectra was found to be similar to that of the oxidation of Si(111)77 surfaces. Also the molecular oxygen was appeared after the initial surface oxides, indicating that this was not a precursor for dissociation oxygen adsorption onto the clean surface. We have proposed presumable structural models for atomic configurations, where the molecular oxygen was resided on the oxidized silicon with two oxygen atoms at the backbonds.

Neutron scattering study of spin fluctuations in LaSrCuO by four-dimensional mapping of neutron cross-sections using the 4SEASONS chopper spectrometer

Wakimoto, Shuichi; Ikeuchi, Kazuhiko*; Arai, Masatoshi; Fujita, Masaki*; Kajimoto, Ryoichi; Kawamura, Sho*; Matsuura, Masato*; Nakajima, Kenji; Yamada, Kazuyoshi*

JPS Conference Proceedings (Internet), 8, p.034013_1 - 034013_6, 2015/09

https://doi.org/10.7566/JPSCP.8.034013

Resonant inelastic X-ray scattering study of intraband charge excitations in hole-doped high- cuprates

Wakimoto, Shuichi; Ishii, Kenji; Kimura, Hiroyuki*; Ikeuchi, Kazuhiko*; Yoshida, Masahiro*; Adachi, Tadashi*; Casa, D.*; Fujita, Masaki*; Fukunaga, Yasushi*; Gog, T.*; et al.

Physical Review B, 87(10), p.104511_1 - 104511_7, 2013/03

https://doi.org/10.1103/PhysRevB.87.104511

Ni-substitution effects on the spin dynamics and superconductivity in LaSrCuO

Matsuura, Masato*; Fujita, Masaki*; Hiraka, Haruhiro*; Kofu, Maiko*; Kimura, Hiroyuki*; Wakimoto, Shuichi; Perring, T. G.*; Frost, C. D.*; Yamada, Kazuyoshi*

Physical Review B, 86(13), p.134529_1 - 134529_8, 2012/10

https://doi.org/10.1103/PhysRevB.86.134529

Research on glass cells for He neutron spin filters

Sakaguchi, Yoshifumi; Kira, Hiroshi; Oku, Takayuki; Shinohara, Takenao; Suzuki, Junichi; Sakai, Kenji; Nakamura, Mitsutaka; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; et al.

Physica B; Condensed Matter, 406(12), p.2443 - 2447, 2011/06

https://doi.org/10.1016/j.physb.2010.12.020

Characterization of glasses for He neutron spin filter cells

Sakaguchi, Yoshifumi; Kira, Hiroshi; Oku, Takayuki; Shinohara, Takenao; Suzuki, Junichi; Sakai, Kenji; Nakamura, Mitsutaka; Suzuya, Kentaro; Arai, Masatoshi; Takeda, Masayasu; et al.

Nuclear Instruments and Methods in Physics Research A, 634(1, Suppl.), p.S122 - S125, 2011/04

Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in BiPbSrCuFeO

Wakimoto, Shuichi; Hiraka, Haruhiro*; Kudo, Kazutaka*; Okamoto, Daichi*; Nishizaki, Terukazu*; Kakurai, Kazuhisa; Hong, T.*; Zheludev, A.*; Tranquada, J. M.*; Kobayashi, Norio*; et al.

Physical Review B, 82(6), p.064507_1 - 064507_7, 2010/08

https://doi.org/10.1103/PhysRevB.82.064507

no abstracts in English

Fe-doping effects on magnetism in hole-type superconductors of (Bi,Pb)SrCuO

Hiraka, Haruhiro*; Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; Matsumura, Daiju; Nishihata, Yasuo; Mizuki, Junichiro; Yamada, Kazuyoshi*

Journal of Physics; Conference Series, 200, p.012059_1 - 012059_4, 2010/02

https://doi.org/10.1088/1742-6596/200/1/012059

We studied Fe-dopant effects on spin correlations in BiPbSrCuO. Magnetic neutron elastic scattering, which is absent in a pristine sample, has been observed at incommensurate positions with an incommensurability of 0.2. Surprisingly, this anomalously large follows a linear relation even in the overdoped region, unlike for LaSrCuO. We discuss this specific feature observed in the overdoped phase from a dynamical stripe viewpoint.