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RBS study of disordering of Fe$$_{3-x}$$Mn$$_{x}$$Si/Ge(111) heteroepitaxial interfaces

野口 雄也*; 平田 智昭*; 川久保 雄基*; 鳴海 一雅; 境 誠司; 前田 佳均

Physica Status Solidi (C), 10(12), p.1732 - 1734, 2013/12

 被引用回数:0 パーセンタイル:100

We have investigated thermal disordering and instability of Fe$$_{2}$$MnSi (FMS) (111)/Ge(111) heterointerfaces by Rutherford-backscattering spectrometry (RBS), and found pronounced degradation of axial orientation which appears as increase of the minimum yield of RBS when the FMS samples are annealed above 300$$^{circ}$$C. Analysis of interdiffusion at the heterointerface reveals that the disordering mainly comes from interdiffusion between Fe and Ge atoms. This situation is the same as that observed in off-stoichiometric Fe$$_{3}$$Si, ${it i.e.}$, Fe$$_{4}$$Si, but far from that in stoichiometric Fe$$_{3}$$Si.


Ion beam analysis of quaternary Heusler alloy Co$$_{2}$$(Mn$$_{1-x}$$Fe$$_{x}$$)Si(111) epitaxially grown on Ge(111)

川久保 雄基*; 野口 雄也*; 平田 智昭*; 鳴海 一雅; 境 誠司; 山田 晋也*; 浜屋 宏平*; 宮尾 正信*; 前田 佳均

Physica Status Solidi (C), 10(12), p.1828 - 1831, 2013/12

 被引用回数:0 パーセンタイル:100

We have investigated crystal quality of Co$$_{2}$$(Mn$$_{1-x}$$Fe$$_{x}$$)Si (CMFS) epitaxially grown on Ge(111) by using Rutherford-backscattering spectrometry and an axial-ion-channeling technique. It was found that the CMFS/Ge and Co$$_{2}$$FeSi (CMFS with x = 1)/Ge have larger static atomic displacement than Fe-based ternary Heusler alloy Fe$$_{2}$$MnSi and Fe$$_{2}$$CoSi/Ge(111). Quaternary alloys may be affected by increase of mixing entropy. Significant disordering at the interface of CMFS with x = 0.75 was found, and discussed on the basis of thermodynamics.


Cluster effect on damage accumulation in a Si crystal bombarded with 10-540-keV C$$_{60}$$ ions

鳴海 一雅; 楢本 洋*; 山田 圭介; 千葉 敦也; 齋藤 勇一; 前田 佳均

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 166, 2013/01

本研究では、10-100keV領域のC$$_{60}$$イオン衝撃の非線形効果を明らかにすることを目的としている。室温でSi結晶に10-540keV C$$_{60}$$イオンを照射し、1個のC$$_{60}$$イオン衝撃により格子位置から変位したSi原子数$${it N}$$$$_{D60}$$をラザフォード後方散乱/チャネリング法で評価したところ、照射損傷の照射量依存性がイオントラック的描像で説明できることがわかった。さらに、入射C原子1個あたりの変位したSi原子数の比$${it N}$$$$_{D60}$$/(60$$times$$$${it N}$$$$_{D1}$$)を使って非線形効果を評価した。ここで、$${it N}$$$$_{D1}$$は、同じ速度のCイオン衝撃により格子位置から変位したSi原子数であり、SRIM2008を使って求めた。比はC$$_{60}$$イオンのエネルギーに依存し、100keV近辺で最大になった。この比のエネルギー依存性、すなわち非線形効果のエネルギー依存性は、核的阻止能とSi中でのC原子間距離の広がりによって定性的に説明できる。


Photoluminescence properties of carbon-doped $$beta$$-FeSi$$_{2}$$ nanocrystals

前田 佳均; 西村 健太郎*; 中島 孝仁*; 松倉 武偉*; 鳴海 一雅; 境 誠司

Physica Status Solidi (C), 9(10-11), p.1884 - 1887, 2012/10

 被引用回数:4 パーセンタイル:6.98



Enhancement of IR light emission from $$beta$$-FeSi$$_{2}$$ nanocrystals embedded in Si

前田 佳均; 西村 健太郎*; 中島 孝仁*; 松倉 武偉*; 鳴海 一雅; 境 誠司

Physica Status Solidi (C), 9(10-11), p.1888 - 1891, 2012/10

 被引用回数:3 パーセンタイル:10.67



Energy dependence of nonlinear effects of sputtering yields of Si bombarded with 10-540-keV C$$_{60}$$ ions

鳴海 一雅; 楢本 洋*; 山田 圭介; 齋藤 勇一; 千葉 敦也; 高橋 康之*; 前田 佳均

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 155, 2012/01

10-540keV C$$_{60}$$イオンをSiに照射した場合のスパッタリング収量を測定した。C$$_{60}$$イオン照射によるSiのスパッタリング収量は100keV近辺で最大になり、C$$_{60}$$イオン1個あたり約600個となった。Sigmundの理論及びSRIM2008によって求めた同速度のC単原子イオンによるスパッタリング収量と比較したところ顕著な非線形効果を見いだした。非線形効果の指標となる入射C原子あたりのスパッタリング収量の比は最大で約12になり、一方10keVではほぼ1となった。さらに、クラスターイオンの構成原子数を$${it n}$$とすると、スパッタリング収量は$${it n}$$$$^{2}$$には依存しないことがわかった。以上の結果は、非線形効果の起源が熱スパイクモデルではなく、密な衝突カスケードによるものであることを支持する。


Ion channeling study of epitaxy of iron based Heusler alloy films on Ge(111)

前田 佳均; 鳴海 一雅; 境 誠司; 寺井 慶和*; 浜屋 宏平*; 佐道 泰造*; 宮尾 正信*

Thin Solid Films, 519(24), p.8461 - 8467, 2011/10

 被引用回数:6 パーセンタイル:66.41(Materials Science, Multidisciplinary)

We investigate the axial orientation of epitaxy of Fe$$_{2}$$CoSi with a (A, C) site preference on Ge(111) by using ion channeling, and discuss dominant factors for epitaxy of Fe$$_{2}$$MnSi and Fe$$_{2}$$CoSi on Ge(111). We conclude that each dominant factor of epitaxy of Fe$$_{2}$$MnSi and Fe$$_{2}$$CoSi on Ge(111) comes from an atomic displacement due to different preference of site occupations.


Effect of cotunneling and spin polarization on the large tunneling magnetoresistance effect in granular C$$_{60}$$-Co films

境 誠司; 三谷 誠司*; 菅井 勇; 高梨 弘毅; 松本 吉弘; 圓谷 志郎; 楢本 洋*; Avramov, P.; 前田 佳均

Physical Review B, 83(17), p.174422_1 - 174422_6, 2011/05

 被引用回数:8 パーセンタイル:58.73(Materials Science, Multidisciplinary)

Magnetotransport properties of the granular C$$_{60}$$-Co films are investigated over the broad bias voltage range from the region near zero bias by using the samples with the CPP (current-perpendicular-to-plane) geometry. It is revealed that the granular C$$_{60}$$-Co films show the I-V characteristics ascribed to cotunneling whose magnitudes are comparable to other molecular-based granular films. Furthermore, by considering the contribution of cotunneling on the magnitude of the TMR effect, it is successfully demonstrated that the tunnelling electrons generated at the interface between Co nanoparticles and a C$$_{60}$$-based matrix (C$$_{60}$$-Co compound) in the films have a significantly higher spin polarization (50-80%) than those in Co crystal and at the Al-oxide/Co interface. The present results clearly suggest that the high interfacial spin polarization is the most important cause of the large TMR effect in the granular C$$_{60}$$-Co films, in spite of the cotunneling-induced enhancement.


Interface properties of Ag and Au/graphene heterostructures studied by micro-Raman spectroscopy

圓谷 志郎; 境 誠司; 松本 吉弘; 楢本 洋*; Hao, T.; 前田 佳均

Japanese Journal of Applied Physics, 50(4), p.04DN03_1 - 04DN03_5, 2011/04

 被引用回数:4 パーセンタイル:77.58(Physics, Applied)

We have studied the influence of the interface formation of graphene with noble metals (Ag and Au) on its vibrational properties by using confocal micro-Raman spectroscopy. The interactions at the metal/graphene interface are investigated by comparing the results from two different regions, the heterostructure and pristine graphene regions, with and without noble metals on the same graphene sheet. In Ag/graphene, the Raman signal intensity was increased by the surface enhanced Raman scattering process, and the enhanced signals are found to be composed of the broadened D and G peak components emitted from the Ag/graphene interface. The precise evaluation of graphene-layer-number-dependence of the D and G bands revealed that the disordered graphitic carbons were adhered on the glass substrate during the sample preparation by the micromechanical cleavage method. In the 2D band, no obvious peak shift induced by the heterostructure formation was observed in Ag/graphene, whereas a large shift (more than $$sim$$15 cm$$^{-1}$$) was observed at Au/single layer graphene. This is considered to be due to the difference in the amount of the doped carriers in graphene between two heterostructures.


Determination of silicon vacancy in ion-beam synthesized $$beta$$-FeSi$$_{2}$$

前田 佳均; 市川 貴之*; 上西 隆文*; 鳴海 一雅

Physics Procedia, 11, p.83 - 86, 2011/00

 被引用回数:0 パーセンタイル:100

Using Rutherford backscattering spectrometry (RBS), we can deduce the concentration of Si vacancy and its depth profile in the $$beta$$-FeSi$$_{2}$$ layer and find confirmation of the effect of the thermal annealing on reduction of the Si vacancy. The concentration of Si vacancy at the inside of $$beta$$-FeSi$$_{2}$$ is reduced after the long annealing. Contrary to the inside, at the interface the Si vacancy remains at $$sim$$1.5 at% even after the annealing for 360 min. Moreover we find consistency of our analysis of Si vacancy on an evident correlation between the reduction of Si vacancy and improvement of crystallinity (decrease of the $$chi$$$$_{min}$$) by the annealing.


Interface properties of metal/graphene heterostructures studied by micro-Raman spectroscopy

圓谷 志郎; 境 誠司; 松本 吉弘; 楢本 洋*; Hao, T.; 前田 佳均

Journal of Physical Chemistry C, 114(47), p.20042 - 20048, 2010/11

 被引用回数:34 パーセンタイル:25.4(Chemistry, Physical)

Studies are conducted for the influence of the interface formation of graphene with various transition metals on its vibrational properties by using confocal micro-Raman spectroscopy. Comparative analysis for two different regions of single-layer graphene (SLG) and multilayer graphene (MLG) fabricated within an identical graphene sheet enables us to investigate the interactions at and the doping effect from the metal/graphene interface as a function of the layers number of graphene without the influence of the unintentional doping. Confirmed dependences of the peaks shifts of the Raman bands (D, G and 2D bands) on the graphene layers number and metal species (Co, Ni and Au) reveal that the interfacial interactions are dramatically different between single layer and multilayer graphenes. In the metal/MLG heterostructures, the Raman band shifts are reasonably attributed to carrier doping from metals. In the metal/SLG heterostructures, significant differences from the metal/MLG heterostructures were observed for the Raman parameters of the G and 2D bands. It is suggested that there exist strong interactions at the metal/SLG interfaces different from those at the metal/MLG interfaces.


Composition dependence of magnetic and magnetotransport properties in C$$_{60}$$-Co granular thin films

菅井 勇*; 境 誠司; 松本 吉弘; 楢本 洋*; 三谷 誠司*; 高梨 弘毅; 前田 佳均

Journal of Applied Physics, 108(6), p.063920_1 - 063920_7, 2010/09

 被引用回数:7 パーセンタイル:64.94(Physics, Applied)

Composition dependence of magnetic and magnetotransport properties in C$$_{60}$$Co$$_{x}$$ thin films exhibiting large magnetoresistance TMR effect was investigated in the Co composition range of x=8-20, where x denotes the number of Co atoms per C$$_{60}$$ molecule. The composition dependence of magnetic property revealed a structural transition from well-defined granular structures in the range of x=8-17 to magnetically and electronically coupled states of Co nanoparticles over x=17. As a result of the structural change, the MR behavior became different between the two composition regions separated at x=17. It is found that the zero-bias MR ratio and also the strength of the voltage dependence are in proportion to the charging energy to Co nanoparticles in the samples with well-defined granular structures. The present results indicate that the charging effect of Co nanoparticles plays an important role in the anomalously large MR effect of C$$_{60}$$-Co granular films.


RBS study of diffusion under strong centrifugal force in bimetallic Au/Cu thin films

Hao, T.; 小野 正雄; 岡安 悟; 境 誠司; 鳴海 一雅; 平岩 佑介*; 楢本 洋*; 前田 佳均

Nuclear Instruments and Methods in Physics Research B, 268(11-12), p.1867 - 1870, 2010/06

 被引用回数:3 パーセンタイル:68.37(Instruments & Instrumentation)

We investigate firstly the effect of strong centrifugal force ($$sim$$10$$^{6}$$ G, G = 9.8 m/s$$^{2}$$: SCF) on diffusion behavior in bimetallic Au/Cu thin films. Then SCF were applied with 0.61$$times$$10$$^{6}$$ G in the directions inward (+MG) and outward (-MG) $$alpha$$-Al$$_{2}$$O$$_{3}$$ substrates at 220$$^{circ}$$C for 140 minutes. The Rutherford Backscattering Spectrometry (RBS: 2.7 MeV $$^{4}$$He$$^{+}$$) was used to evaluate the depth profiles of gold and copper atoms for the bimetallic Au/Cu thin films. The results show that in the present condition the diffusion of copper atoms through the gold layer is main process but the diffusion of gold atoms into the copper layers is unobvious for all the cases. Furthermore, it was found that SCF of +MG do not affect distinctly the diffusion of copper atoms through the gold layer, while SCF of -MG can promote damatically the diffusion of copper atoms through gold.


Vicinage effect on secondary-electron emission in the forward direction from amorphous carbon foils induced by swift C$$_{2}$$$$^{+}$$ ions

高橋 康之; 鳴海 一雅; 千葉 敦也; 齋藤 勇一; 山田 圭介; 石川 法人; 須貝 宏行; 前田 佳均

EPL; A Letters Journal Exploring the Frontiers of Physics, 88(6), p.63001_1 - 63001_6, 2009/12

 被引用回数:6 パーセンタイル:55.09(Physics, Multidisciplinary)



X-ray absorption spectroscopy and magnetic circular dichroism in codeposited C$$_{60}$$-Co films with giant tunnel magnetoresistance

松本 吉弘; 境 誠司; 高木 康多*; 中川 剛志*; 横山 利彦*; 島田 敏宏*; 三谷 誠司*; 楢本 洋*; 前田 佳均

Chemical Physics Letters, 470(4-6), p.244 - 248, 2009/03

 被引用回数:17 パーセンタイル:43(Chemistry, Physical)



Theoretical DFT study of atomic structure and spin states of the Co$$_{x}$$(C$$_{60}$$)$$_{n}$$ (x=3-8, n=1,2) somplex nanoclusters

Avramov, P.*; 境 誠司; 楢本 洋*; 鳴海 一雅; 松本 吉弘; 前田 佳均

Journal of Physical Chemistry C, 112(36), p.13932 - 13936, 2008/08

 被引用回数:4 パーセンタイル:81(Chemistry, Physical)

Co及びC$$_{60}$$Co複合クラスターの原子構造とスピン状態について第一原理GGA計算による解析を行った。孤立Coクラスターのスピン状態について、ヤンテラー歪の効果により高スピン状態を有する低対称なクラスターが生成することが示された。C60Co複合クラスターについて、C$$_{60}$$分子の6員環とCoクラスターのCo原子間に$$eta$$2, $$eta$$2'もしくは$$eta$$1型の配位結合が生じることで複合クラスターが安定化することが示された。その場合のCo原子当のスピン磁気モーメントは、Coクラスター部位のサイズに対して単調でない依存性を示すことがわかった。


The Electronic structures of fullerene/transition-metal hybrid material

松本 吉弘; 境 誠司; 楢本 洋*; 平尾 法恵*; 馬場 祐治; 島田 敏宏*; 菅井 勇; 高梨 弘毅; 前田 佳均

Materials Research Society Symposium Proceedings, Vol.1081 (Internet), 6 Pages, 2008/03



Giant tunnel magnetoresistance in codeposited fullerene-cobalt films in the low bias-voltage regime

境 誠司; 菅井 勇; 三谷 誠司*; 高梨 弘毅; 松本 吉弘; 楢本 洋*; Avramov, P.; 岡安 悟; 前田 佳均

Applied Physics Letters, 91(24), p.242104_1 - 242104_3, 2007/12

 被引用回数:30 パーセンタイル:24.66(Physics, Applied)

Magnetotransport properties in the low bias-voltage regime were investigated for co-deposited C$$_{60}$$-Co films. A giant tunnel magnetoresistance (MR) ratio ($$Delta$$$$R$$/$$R$$$$_{max}$$) of 80%, which is the highest in ferromagnetic metal/organic molecule systems, was found at low temperatures. The observed bias-voltage dependence of the MR ratio is expressed by an unusual exponential form, suggesting that the MR ratio of nearly 100% can be realized in the low bias-voltage limit.


Axial orientation of molecular-beam-epitaxy-grown Fe$$_{3}$$Si/Ge hybrid structures and its degradation

前田 佳均; 上西 隆文*; 鳴海 一雅; 安藤 裕一郎*; 上田 公二*; 熊野 守*; 佐道 泰造*; 宮尾 正信*

Applied Physics Letters, 91(17), p.171910_1 - 171910_3, 2007/10

 被引用回数:30 パーセンタイル:24.66(Physics, Applied)



Comparative study of structures and electrical properties in cobalt-fullerene mixtures by systematic change of cobalt content

境 誠司; 楢本 洋*; Avramov, P.; 矢板 毅; Lavrentiev, V.; 鳴海 一雅; 馬場 祐治; 前田 佳均

Thin Solid Films, 515(20-21), p.7758 - 7764, 2007/07

 被引用回数:22 パーセンタイル:30.43(Materials Science, Multidisciplinary)


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