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-Al
O
(0001) for use as an adsorbent圓谷 志郎*; 本田 充紀; 滝沢 優*; 好田 誠*
Beilstein Journal of Nanotechnology (Internet), 16, p.1082 - 1087, 2025/07
Graphene oxide (GO) is expected to be one of the most promising adsorbents for metal ions, including radioactive nuclides in aqueous solutions. Large-area and single-layer graphene oxide (SLGO) grown on -AlO(0001) was used as a model structure of GO since the aggregation and re-stacking of the GO sheets prevent the adequate analysis of the adsorption state. The SLGO film was obtained by oxidizing monolayer graphene grown by metal-free chemical vapor deposition on the -AlO(0001) surface, and the adsorption state was determined by surface analytical techniques. It was clarified that Cs adsorbs on oxygen functional groups by substituting with H atoms from carboxyl and hydroxy groups. It is also estimated that the weight adsorption capacity of SLGO in the 1.0 mol/L-Cs aqueous solution is as much as approximately 70 wt%. It has been demonstrated that GO has great potential to be a promising adsorbent for Cs in aqueous solutions.
圓谷 志郎*; 本田 充紀; 水口 将輝*; 渡邉 英雄*; 大島 武*; 好田 誠*
ACS Omega (Internet), 10(21), p.21537 - 21542, 2025/06
Heteroatom doping into graphene has attracted wide attention for tailoring electronic, physical, and chemical properties of graphene. In order to achieve the application of doped graphene in an effective manner, it is essential to use films with a large area and a precise number of layers. Therefore, it is necessary to develop a technique for heteroatom doping directly into CVD-grown large-area graphene. In this study, high-energy heavy ion irradiation to the heterostructure of the KCl layer and the CVD-grown single-layer graphene film allowed the formation of Cl-C chemical bonds. The spectroscopic analysis indicated that the doping of graphene by Cl atoms, at a concentration of 10.2 atom %, had occurred as a result of the irradiation of 3.0 MeV Ni
ions at a fluence of up to 10
ions/cm
. It is shown that Cl atoms are chemically adsorbed on graphene by the formation of C-Cl bonds with the chemical reconstruction of graphene from sp- to sp
-hybridization.
深谷 有喜; 圓谷 志郎*; 境 誠司*
Physical Review B, 108(15), p.155422_1 - 155422_6, 2023/10
被引用回数：2 パーセンタイル：19.47(Materials Science, Multidisciplinary)本研究では、全反射高速陽電子回折を用いて、Ag及びAu原子のインターカレーションによるCo(0001)表面上の単層グラフェンの界面構造変化について調べた。動力学的回折理論に基づく構造解析の結果、400
C以上のアニールによりAg及びAu原子はインターカレーションを起こし、グラフェンの高さが2.04
から3.24 (Ag)および3.32 (Au)に変位することがわかった。700Cでのさらなるアニールにより、Ag原子はデインターカレーションを起こし、グラフェンの高さがインターカレーション前のものに戻る。一方、Au原子では900C以上にアニールしてもデインターカレーションを起こさない。この違いは、Ag及びAu原子の熱脱離過程における活性化エネルギーの差によって説明できる。
圓谷 志郎*; 佐藤 真一郎*; 本田 充紀; 鈴木 千尋*; 田口 富嗣*; 山本 春也*; 大島 武*
Radiation Physics and Chemistry, 199, p.110369_1 - 110369_7, 2022/10
被引用回数：1 パーセンタイル：11.89(Chemistry, Physical)SiへのNiイオンビーム照射によるNiシリサイド合成は、局所構造の形成が可能、イオンビームの制御が可能、熱処理なしでシリサイドが形成可能、得られる試料の再現性が高い、などの利点から注目されている。本研究では、3.0MeVのNiイオンを注入したSiの局所的な原子構造を調査した。Ni K吸収端蛍光収量拡張X線吸収微細構造解析の結果、Ni原子は照射初期に金属的な面心立方NiとNiSi相の混合構造を持っており、イオン照射量が10個・cm Si以上になるとNiSiの形成が著しく促進することが明らかになった。構造転移のイオン照射量とSiアモルファス化臨界量(7.1
10
ions・cm)の一致から、Ni照射SiにおけるNiSi相の合成にはSiのアモルファス化が重要であると結論づけた。
-AlO(0001)圓谷 志郎*; 本田 充紀; 楢本 洋*; Li, S.*; 境 誠司*
Surface Science, 704, p.121749_1 - 121749_6, 2021/02
被引用回数：7 パーセンタイル：34.53(Chemistry, Physical)グラフェンは、ナノエレクトロニクスやスピントロニクスの最も有望な材料の一つとして期待されている。グラフェンを用いたデバイスの多くは、グラフェンチャンネルが絶縁体基板上に配置されている。そのため、グラフェンと絶縁体表面との界面相互作用の研究は非常に重要である。本研究では、-AlO(0001)上に転写されたグラフェンの垂直配置を通常入射X線定在波法(NIXSW)によって研究した。NIXSWプロファイルの解析から、グラフェン層は-AlO(0001)表面から3.57()上に位置し、これはグラファイトの層間距離である3.356()より大きいことが明らかにされた。マイクロラマン分光法では、転写されたグラフェンのホール濃度の空間分布が限定的であることが示された。本研究により、サファイア基板上に転写したグラフェンを真空アニールすることで、有機化合物などの残留汚染物のない原子レベルで平坦な表面が得られ、グラフェンに正孔がドープされることが明らかになった。
圓谷 志郎*; 本田 充紀; 下山 巖; Li, S.*; 楢本 洋*; 矢板 毅; 境 誠司*
Japanese Journal of Applied Physics, 57(4S), p.04FP04_1 - 04FP04_4, 2018/04
被引用回数：4 パーセンタイル：16.31(Physics, Applied)Graphene oxide (GO) with a large surface area was synthesized by the direct growth of GO on porous alumina using chemical vapor deposition to study the Cs adsorption mechanism in aqueous solutions. Electronic structure analysis employing in situ near-edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy measurements clarifies the Cs atoms bond via oxygen functional groups on GO in the aqueous solution. The Cs adsorption capacity was found to be as high as 650-850 mg g
, which indicates that the GO/porous alumina acts as an effective adsorbent with high adsorption efficiency for radioactive nuclides in aqueous solutions.
深谷 有喜; 圓谷 志郎; 境 誠司; 望月 出海*; 和田 健*; 兵頭 俊夫*; 社本 真一
Carbon, 103, p.1 - 4, 2016/07
被引用回数：27 パーセンタイル：60.86(Chemistry, Physical)本研究では、全反射高速陽電子回折法を用いて、貴金属および遷移金属基板上のグラフェンの構造を調べた。動力学的回折理論に基づく構造解析から、CuおよびCo基板上のグラフェンの高さをそれぞれ3.34および2.06と決定した。Cu基板上のグラフェンの高さはグラファイトの層間距離に近く、グラフェン・Cu基板間の相互作用は非常に弱いことがわかった。一方、Co基板上のグラフェンの高さは、Cu基板上のものに比べ1以上も低く、Co基板上のグラフェンは基板と強く相互作用していることが実験的に確かめられた。
白 怜士*; 田代 隆治*; 中山 裕康*; 家田 淳一; 圓谷 志郎; 境 誠司; 安藤 和也*
Applied Physics Express, 8(7), p.073009_1 - 073009_3, 2015/07
被引用回数：4 パーセンタイル：16.79(Physics, Applied)Ni
Fe
/Pt二重層の境界面に、単層グラフェン(SLG)を挿入するとスピンポンピングが強力に抑制されることを見いだした。NiFe/Pt二重層におけるスピンポンピングは、強磁性層の磁化緩和を促進させる。このことは、強磁性共鳴線幅のマイクロ波周波数依存性により定量的に評価される。我々は、このスピンポンピングによる磁化緩和の促進が、NiFe/SLG/Pt三重層において消失することを示す。本成果は、単一原子層によってスピンポンピングが遮断されることを示しており、金属系のスピンポンピングにおける界面短距離スピン交換結合の重要性を明らかにするものである。
圓谷 志郎; 楢本 洋*; 境 誠司
Journal of Applied Physics, 117(17), p.17A334_1 - 17A334_4, 2015/05
被引用回数：21 パーセンタイル：61.51(Physics, Applied)Magnetotransport properties were studied for the vertical spin valve devices with two junctions of permalloy electrodes and a few-layer graphene interlayer. The graphene layer was directly grown on the bottom electrode by chemical vapor deposition. X-ray photoelectron spectroscopy showed that the permalloy surface fully covered with a few-layer graphene is kept free from oxidation and contamination even after dispensing and removing photoresist. This enabled fabrication of the current perpendicular to plane spin valve devices with a well-defined interface between graphene and permalloy. Spin-dependent electron transport measurements revealed a distinct spin valve effect in the devices. The magnetotransport ratio was 0.8% at room temperature and increased to 1.75% at 50 K. Linear current-voltage characteristics and resistance increase with temperature indicated that ohmic contacts are realized at the relevant interfaces.
圓谷 志郎; Antipina, L. Y.*; Avramov, P.*; 大伴 真名歩*; 松本 吉弘*; 平尾 法恵; 下山 巖; 楢本 洋*; 馬場 祐治; Sorokin, P. B.*; et al.
Nano Research, 8(5), p.1535 - 1545, 2015/05
被引用回数：29 パーセンタイル：71.21(Chemistry, Physical)Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal atomic arrangement and electronic properties of the coherent heterostructure of single-layer graphene and -AlO(0001). In the atomic arrangement analysis of single-layer graphene on -AlO(0001), we observed apparently contradicting results. The in-plane analysis shows that single-layer graphene grows not in the single-crystalline epitaxial manner but in the polycrystalline form with two strongly pronounced preferred orientations. This suggests the relatively weak interfacial interactions to be operative. But, we demonstrate that there exists unusually strong physical interactions between graphene and -AlO(0001), as evidenced by the short vertical distance between graphene and -AlO(0001) surface. The interfacial interactions are shown to be dominated by the electrostatic force involved in the graphene 
-system and the unsaturated electrons of the topmost O layer of -AlO(0001) rather than the van der Waals interactions. Such feature causes hole doping into graphene, which gives graphene a chance to slide on the -AlO(0001) surface with a small energy barrier despite the strong interfacial interactions.
Kuzubov, A. A.*; Kovaleva, E. A.*; Avramov, P. V.*; Kuklin, A. V.*; Mikhaleva, N. S.*; Tomilin, F. N.*; 境 誠司; 圓谷 志郎; 松本 吉弘*; 楢本 洋*
Journal of Applied Physics, 116(8), p.084309_1 - 084309_4, 2014/08
被引用回数：9 パーセンタイル：35.30(Physics, Applied)The interaction between carbon and BN nanotubes (NT) and transition metal Co and Ni supports was studied using electronic structure calculations. Several configurations of interfaces were considered, and the most stable ones were used for electronic structure analysis. All NT/Co interfaces were found to be more energetically favorable than NT/Ni, and conductive carbon nanotubes demonstrates lightly stronger bonding than semiconducting ones. The presence of contact-induced spin polarization was established for all nanocomposites. It was found that the contact-induced polarization of BNNT leads to the appearance of local conductivity in the vicinity of the interface while the rest of the nanotube lattice remains to be insulating.
Avramov, P. V.*; Kuzubov, A. A.*; 境 誠司; 大伴 真名歩*; 圓谷 志郎; 松本 吉弘*; Eleseeva, N. S.*; Pomogaev, V. A.*; 楢本 洋*
Journal of Porphyrins and Phthalocyanines, 18(7), p.552 - 568, 2014/07
被引用回数：1 パーセンタイル：4.86(Chemistry, Multidisciplinary)A wide variety of planar and curved fused porphyrin/metalloporphyrin nanoclusters have been studied at the LC-GGA DFT level. It was found that curved and hollow-caged 0D and 1D nanoclusters are metastable and bear unique atomic and electronic structure and mechanical properties. Under different types of mechanical loads the nanoclusters display ultrastrong and superelastic properties. The curvature of the hollow cage nanoclusters leads to the redistribution of the metal d states near the Fermi level. The extremely high spin states allow one to use Fe-porphyrin nanoclusters as molecular supermagnets and logic quantum gates for holonomic quantum computations.
大伴 真名歩; 山内 泰*; Kuzubov, A. A.*; Eliseeva, N. S.*; Avramov, P.*; 圓谷 志郎; 松本 吉弘; 楢本 洋*; 境 誠司
Applied Physics Letters, 104(5), p.051604_1 - 051604_4, 2014/02
被引用回数：12 パーセンタイル：44.07(Physics, Applied)六方晶窒化ホウ素(h-BN)はグラフェン・スピントロニクスのトンネルバリア材料として有望視されている。本研究ではスピン偏極準安定ヘリウム脱励起分光法(SPMDS)を用いて、Ni(111)上の単層h-BNのスピン分解バンド構造を調べた。SPMDSの最表面敏感性により、Ni 3
ピークの重複を受けずに部分的に占有されたギャップ内順位を検出できた。さらにこのギャップ内順位は大きなスピン偏極を持ち、Niの多数スピン側に偏極していることが示された。この正のスピン偏極は、h-BN/Ni(111)界面における-軌道混成によるものであると帰属できた。
圓谷 志郎; 倉橋 光紀*; Sun, X.*; 山内 泰*
Carbon, 61, p.134 - 139, 2013/09
被引用回数：17 パーセンタイル：46.14(Chemistry, Physical)The spin-resolved electronic structure of graphene on Ni(111) was investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). Graphene was grown epitaxially on a Ni(111) single-crystalline surface using the ultra high vacuum chemical vapor deposition technique with benzene vapor as a precursor. At 50 L (510
Torr sec), a single epitaxial layer of graphene was formed, but no further growth was observed at higher exposure. The spin-summed spectrum of graphene/Ni(111) had a new peak at the Fermi level and three weak features corresponding to the molecular orbitals of graphene. Spin asymmetry analysis of the SPMDS spectra revealed that the spin polarization of the electronic states shown by the new peak was parallel to the majority spin of the Ni substrate. The appearance and spin polarization of the new electronic states are discussed in terms of the hybridization of graphene pi orbitals and Ni d orbitals.
松本 吉弘; 圓谷 志郎; 小出 明広*; 大伴 真名歩; Avramov, P.; 楢本 洋*; 雨宮 健太*; 藤川 高志*; 境 誠司
Journal of Materials Chemistry C, 1(35), p.5533 - 5537, 2013/09
被引用回数：34 パーセンタイル：76.94(Materials Science, Multidisciplinary)The spin-electronic structures across the interface between single-layer graphene and a Ni(111) thin film are explored by employing the depth-resolved X-ray absorption and magnetic circular dichroism spectroscopy with the atomic layer resolution. The depth-resolved Ni L-edge analysis clarifies that the Ni atomic layers adjacent to the interface show a transition of the spin orientation to the perpendicular one in contrast with the in-plane one in the bulk region. The C K-edge analysis reveals the intensifying of the spin-orbital interactions induced by the 
-d hybridization at the interface as well as out-of-plane spin polarization at the band region of graphene. The present study indicates the importance of the interface design at the atomic layer level for graphene-based spintronics.
interface in the Fe-doped C film境 誠司; 松本 吉弘; 大伴 真名歩; 圓谷 志郎; Avramov, P.; Sorokin, P. B.*; 楢本 洋*
Synthetic Metals, 173, p.22 - 25, 2013/06
被引用回数：3 パーセンタイル：14.00(Materials Science, Multidisciplinary)A process of tunneling conduction and the spin-dependent resistivity change (so-called tunneling magnetoresitance effect) in the Fe-doped C film with a granular structure is investigated for the current-into-plane device. Cooperative tunneling (cotunneling) through several Fe nanoparticles is suggested to be operative at temperatures lower than 20 K. By considering the effect of cotunneling on the magnetoresistance ratio, it is successfully shown that the spin polarization of tunneling electrons generated at the Fe/C interface is much higher than that in Fe crystal at low temperature in a similar fashion to that at the Co/C interface in the Co-doped C films. A strong temperature dependence of spin polarization is observed, suggesting possible influences by the thermally-induced disorders ascribed in the Fe atoms bonded with C in the C-Fe compound.
-BN/Ni nanocompositesAvramov, P.; Kuzubov, A. A.*; 境 誠司; 大伴 真名歩; 圓谷 志郎; 松本 吉弘; 楢本 洋*; Eliseeva, N. S.*
Journal of Applied Physics, 112(11), p.114303_1 - 114303_10, 2012/12
被引用回数：18 パーセンタイル：56.97(Physics, Applied)Atomic and electronic structure of graphene/Ni(111), -BN/Ni(111) and graphene/-BN/Ni(111) nanocomposites with different numbers of graphene and -BN layers and in different mutual arrangements of graphene/Ni and -BN/Ni at the interfaces was studied using LDA/PBC/PW technique. For the sake of comparison, corresponding graphene, -BN and graphene/-BN structures without the Ni plate were calculated using the same technique. It was suggested that C-
:C-
and N-:B- configurations are energetically favorable for the graphene/Ni and -BN/Ni interfaces, respectively. The Ni plate was found to induce a significant degree of spin polarization in graphene and -BN caused by direct exchange interactions of the electronic states located on different fragments.
Avramov, P.; Fedorov, D. G.*; Sorokin, P. B.*; 境 誠司; 圓谷 志郎; 大伴 真名歩; 松本 吉弘; 楢本 洋*
Journal of Physical Chemistry Letters (Internet), 3(15), p.2003 - 2008, 2012/08
被引用回数：38 パーセンタイル：78.59(Chemistry, Physical)The atomic and electronic structure of narrow zigzag nanoribbons with finite length, consisting of graphene terminated by fluorine on one side, hexagonal ()-BN, and -SiC were studied with density functional theory. It is found that the asymmetry of nanoribbon edges causes a uniform curvature of the ribbons due to structural stress in the aromatic ring plane. Narrow graphene nanoribbons terminated with fluorine on one side demonstrate a considerable out-of-plane bend, suggesting that the nanoribbon is a fraction of a conical surface. It is shown that the intrinsic curvature of the narrow nanoribbons destroys the periodicity and results in a systematic cancellation of the dipole moment. The in- and out-of-plane curvature of thin arcs allows their closure in nanorings or cone fragments of giant diameter.
Antipina, L. Y.*; Avramov, P.; 境 誠司; 楢本 洋*; 大伴 真名歩; 圓谷 志郎; 松本 吉弘; Sorokin, P. B.*
Physical Review B, 86(8), p.085435_1 - 085435_7, 2012/08
被引用回数：57 パーセンタイル：86.99(Materials Science, Multidisciplinary)The graphane with chemically bonded alkali metals (Li, Na, K) was considered as potential material for hydrogen storage. The ab initio calculations show that such material can adsorb as many as four hydrogen molecules per Li, Na, and K metal atom. These values correspond to 12.20, 10.33, and 8.56 wt% of hydrogen, respectively, and exceed the DOE requirements. The thermodynamic analysis shows that Li-graphane complex is the most promising for hydrogen storage with ability to adsorb three hydrogen molecules per metal atom at 300 K and pressure in the range of 5-250 atm.
-Co films with current-perpendicular-to-plane geometry境 誠司; 三谷 誠司*; 松本 吉弘; 圓谷 志郎; Avramov, P.; 大伴 真名歩; 楢本 洋*; 高梨 弘毅
Journal of Magnetism and Magnetic Materials, 324(12), p.1970 - 1974, 2012/06
被引用回数：3 パーセンタイル：13.63(Materials Science, Multidisciplinary)Voltage-dependence of the tunneling magnetoresistance effect in the granular C-Co films has been investigated under the current-perpendicular-to-plane geometry. The transport measurements demonstrate that the granular C-Co films show unusually an exponential MR-V dependence. Small characteristic energies of less than 10's meV are derived from the temperature dependences of the characteristic voltage in the exponential relationship. Considering the voltage drops between Co nanoparticles and also the effect of cotunneling on the energy values, the characteristic energies for the voltage-induced degradation of the spin polarization are found to show a satisfactory agreement with that for the thermally-induced one. It can reasonably be expected that the onset of magnetic disorder to the localized d-electron spins at the interface region of the C-Co compound with Co nanoparticles will lead to the unusual voltage and temperature dependence of the MR ratio and the spin polarization.
