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C; Inelastic neutron scattering study玉造 博夢; 村上 洋一*; 倉本 義夫*; 佐賀山 基*; 松浦 直人*; 川北 至信; 松石 聡*; 鷲尾 康仁*; 井下 猛*; 浜田 典昭*; et al.
Physical Review B, 102(22), p.224406_1 - 224406_5, 2020/12
被引用回数：8 パーセンタイル：43.51(Materials Science, Multidisciplinary)Magnetic excitations in layered electride YC have been found by inelastic neutron scattering. We have observed weak but clear magnetic scattering around the wave number 
, but no magnetic order down to the lowest temperature measured (7 K). The imaginary part of the dynamical susceptibility deduced is well described by the Lorentz function of energy 
for each momentum 
. The width 
of the Lorentzian is proportional to 
with 
at 
K. We have also found that with increasing the magnetic form factor decays faster than that of a 
electron in a single Y atom, which indicates a more extended magnetic moment in YC. These results provide experimental evidence that the itinerant magnetism in YC originates from the anionic electrons that reside in the interlayers. The Curie-Weiss-like behavior of the magnetic susceptibility reported in YC is ascribed to the mode coupling effects of spin fluctuations.
鈴木 秀俊*; 仲田 侑加*; 高橋 正光; 池田 和磨*; 大下 祥雄*; 諸原 理*; 外賀 寛崇*; 森安 嘉貴*
AIP Advances (Internet), 6(3), p.035303_1 - 035303_6, 2016/03
被引用回数：4 パーセンタイル：19.01(Nanoscience & Nanotechnology)The formation and evolution of rotational twin (TW) domains introduced by a stacking fault during molecular-beam epitaxial growth of GaAs on Si (111) substrates were studied by in situ X-ray diffraction. To modify the volume ratio of TW to total GaAs domains, GaAs was deposited under high and low group V/group III (V/III) flux ratios. For low V/III, there was less nucleation of TW than normal growth (NG) domains, although the NG and TW growth rates were similar. For high V/III, the NG and TW growth rates varied until a few GaAs monolayers were deposited; the mean TW domain size was smaller for all film thicknesses.
X-ray diffraction下村 憲一*; 鈴木 秀俊*; 佐々木 拓生; 高橋 正光; 大下 祥雄*; 神谷 格*
Journal of Applied Physics, 118(18), p.185303_1 - 185303_7, 2015/11
被引用回数：9 パーセンタイル：36.75(Physics, Applied)Direct measurements on the growth of InAs quantum dots (QDs) and various cap layers during molecular beam epitaxy are performed by X-ray diffraction (XRD). The evolution of strain induced both in the QDs and cap layers during capping is discussed based on the XRD intensity transients obtained at various lattice constants. Transients with different features are observed from those obtained during InGaAs and GaAs capping, attributed to In-Ga intermixing between the QDs and the cap layer. Photoluminescence wavelength can be tuned by controlling the intermixing and the cap layer thickness. It is demonstrated that such information about strain is useful for designing and preparing novel device structures.
three-dimensional X-ray reciprocal-space mapping of InGaAs multilayer structures grown on GaAs(001) by MBE佐々木 拓生; 高橋 正光; 鈴木 秀俊*; 大下 祥雄*; 山口 真史*
Journal of Crystal Growth, 425, p.13 - 15, 2015/09
被引用回数：4 パーセンタイル：35.32(Crystallography) three-dimensional X-ray reciprocal space mapping (
3D-RSM) was employed for studying molecular beam epitaxial (MBE) growth of InGaAs multilayer structures on GaAs(001). Measuring the symmetric 004 diffraction allowed us to separately obtain film properties of individual layers and to track the real-time evolution of both residual strain and lattice tilting. In two- layer growth of InGaAs, significant plastic relaxation was observed during the upper layer growth, and its critical thickness was experimentally determined. At the same thickness, it was found that the direction of lattice tilting drastically changed. We discuss these features based on the Dunstan model and confirm that strain relaxation in the multilayer structure is induced by two kinds of dislocation motion (dislocation multiplication and the generation of dislocation half-loops).
佐々木 拓生; Norman, A. G.*; Romero, M. J.*; Al-Jassim, M. M.*; 高橋 正光; 小島 信晃*; 大下 祥雄*; 山口 真史*
Physica Status Solidi (C), 10(11), p.1640 - 1643, 2013/11
被引用回数：4 パーセンタイル：82.88(Physics, Applied)Defect characterization in compositionally step graded In
Ga
As layers with different thickness of the overshooting (OS) layer was performed using cathodoluminescence (CL) and transmission electron microscopy (TEM). We found that the type and in-plane distribution of defects generated in the top InGaAs layer grown on step graded layers strongly depend on the thickness of the OS layer. In the thin OS layer, a high density of threading dislocations aligned along [110] was observed. In the thick OS layer, significant line defects associating composition variation were dominantly present. These features on defect type and distribution would relate to strain and configuration of the OS layer.
西 俊明*; 佐々木 拓生; 池田 和磨*; 鈴木 秀俊*; 高橋 正光; 下村 憲一*; 小島 信晃*; 大下 祥雄*; 山口 真史*
AIP Conference Proceedings 1556, p.14 - 17, 2013/09
被引用回数：0 パーセンタイル：0.00(Energy & Fuels) X-ray reciprocal space mapping during InGaAs/GaAs(001) MBE growth is performed to investigate effects of substrate misorientations on crystallographic tilting. It was found that evolution of the crystallographic tilt for the InGaAs films is strongly dependent on both layer structures and substrate misorientations. We discuss these observations in terms of an asymmetric distribution of dislocations.
高橋 正光; 仲田 侑加*; 鈴木 秀俊*; 池田 和磨*; 神津 美和; Hu, W.; 大下 祥雄*
Journal of Crystal Growth, 378, p.34 - 36, 2013/09
被引用回数：5 パーセンタイル：42.01(Crystallography)Epitaxial growth of III-V semiconductors on silicon substrates is a longstanding issue in semiconductor technology including optoelectronics, high-mobility devices and solar cells. In addition to a lattice mismatch of 4%, formation of antiphase domain boundaries makes the growth of GaAs/Si(001) more complicated than that of congeneric combinations, such as Ge/Si(001) and InGaAs/GaAs(001). In the present study, defects in GaAs/Si(001) epitaxial films are investigated by three-dimensional X-ray reciprocal-space mapping technique, which we have successfully applied for InGaAs/GaAs(001) growth. Experiments were carried out at a synchrotron beamline 11XU at SPring-8 using a molecular-beam epitaxy chamber integrated with a multi-axis X-ray diffractometer. Streaky scattering extending from the GaAs 022 peak in the 
directions was observed, indicating development of plane defects, such as facets and stacking faults.
佐々木 拓生*; 下村 憲一*; 鈴木 秀俊*; 高橋 正光; 神谷 格*; 大下 祥雄*; 山口 真史*
Japanese Journal of Applied Physics, 51(2), p.02BP01_1 - 02BP01_3, 2012/02
被引用回数：2 パーセンタイル：8.71(Physics, Applied)In-plane asymmetric strain relaxation in lattice-mismatched InGaAs/GaAs(001) heteroepitaxy is studied by three-dimensional X-ray reciprocal space mapping. Repeating crystal growth and growth interruptions during measurements allows us to investigate whether the strain relaxation is limited at a certain thickness or saturated. We find that the degree of relaxation during growth interruption depends on both the film thickness and the in-plane directions. Significant lattice relaxation is observed in rapid relaxation regimes during interruption. This is a clear indication that relaxation is kinetically limited. In addition, relaxation along the [110] direction can saturate more readily than that along the [
10] direction. We discuss this result in terms of the interaction between orthogonally aligned dislocations.
佐々木 拓生*; 鈴木 秀俊*; 稲垣 充*; 池田 和磨*; 下村 憲一*; 高橋 正光; 神津 美和*; Hu, W.; 神谷 格*; 大下 祥雄*; et al.
IEEE Journal of Photovoltaics, 2(1), p.35 - 40, 2012/01
被引用回数：5 パーセンタイル：22.06(Energy & Fuels)Compositionally step-graded InGaAs/GaAs(001) buffers with overshooting (OS) layers were evaluated by several characterization techniques for higher efficiency metamorphic III-V multijunction solar cells. By high-resolution X-ray diffraction, we found that fully relaxed or tensile strained top layers can be obtained by choosing appropriate OS layer thickness. Moreover, from real-time structural analysis using X-ray reciprocal space mapping ( RSM), it was proved that the top layer is almost strained to the OS layers, and it is independent of the thicknesses of the OS layers. Dislocations in the vicinity of the OS layers were observed by transmission electron microscopy, and the validity of results of RSM was confirmed from the viewpoint of misfit dislocation behavior. Finally, by photoluminescence measurements, we showed that tensile strained top layers may be suitable for the improvement of minority-carrier lifetime.
佐々木 拓生*; 鈴木 秀俊*; 高橋 正光; 大下 祥雄*; 神谷 格*; 山口 真史*
Journal of Applied Physics, 110(11), p.113502_1 - 113502_7, 2011/12
被引用回数：12 パーセンタイル：45.97(Physics, Applied)Dislocation-mediated strain relaxation during lattice-mismatched InGaAs/GaAs(001) heteroepitaxy was studied through X-ray reciprocal space mapping. At the synchrotron radiation facility SPring-8, a hybrid system of molecular beam epitaxy and X-ray diffractometry with a two-dimensional detector enabled us to perform reciprocal space mapping at high-speed and high-resolution. Using this experimental setup, the lattice constants, the diffraction broadenings along in-plane and out-of-plane directions, and the diffuse scattering were investigated. The strain relaxation processes were classified into four thickness ranges with different dislocation behavior. In addition, the existence of transition regimes between the thickness ranges was identified.
佐々木 拓生*; 鈴木 秀俊*; 崔 炳久*; 高橋 正光; 藤川 誠司; 神谷 格*; 大下 祥雄*; 山口 真史*
Journal of Crystal Growth, 323(1), p.13 - 16, 2011/05
被引用回数：20 パーセンタイル：82.65(Crystallography)In
Ga
As/GaAs(001)の分子線エピタキシャル成長中のひずみ緩和の様子をその場X線逆格子マッピングにより解析した。成長温度420, 445, 477
Cにおける残留ひずみ・結晶性の変化の様子が測定された。Dodson-Tsaoの運動学的モデルは、実験による残留ひずみの測定結果とよく一致することがわかった。さらにひずみ緩和過程における転位の運動の温度依存性の解析から、転位の運動の熱励起を議論することが可能になった。
鈴木 秀俊*; 佐々木 拓生*; 崔 炳久*; 大下 祥雄*; 神谷 格*; 山口 真史*; 高橋 正光; 藤川 誠司
Applied Physics Letters, 97(4), p.041906_1 - 041906_3, 2010/07
被引用回数：32 パーセンタイル：74.42(Physics, Applied)Real-time three-dimensional reciprocal space mapping measurement during InGaAs/GaAs(001) molecular beam epitaxial growth has been performed to investigate anisotropy in relaxation processes. Anisotropies, strain relaxation, and crystal quality in [110] and [1
0] directions were simultaneously evaluated via the position and broadness of 022 diffraction. In the small-thickness region, strain relaxation caused by 
-dislocations is higher than that caused by 
-dislocations, and therefore crystal quality along [110] is worse than that along [10]. Rapid relaxation along both [110] and [10] directions occurs at almost the same thickness. After rapid relaxation, anisotropy in strain relaxation gradually decreases, whereas crystal quality along [10] direction, presumably due to -dislocations, becomes better that along [110] direction and the ratio does not decay with thickness.
佐々木 拓生*; 鈴木 秀俊*; 崔 炳久*; 高橋 正光; 藤川 誠司; 大下 祥雄*; 山口 真史*
Materials Research Society Symposium Proceedings, Vol.1268, 6 Pages, 2010/05
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)The in situ X-ray reciprocal space mapping (in situ RSM) of symmetric diffraction measurements during lattice-mismatched InGaAs/GaAs(001) growth were performed to investigate the strain relaxation mechanisms. The evolution of the residual strain and crystal quality were obtained as a function of InGaAs film thickness. Based on the results, the correlation between the strain relaxation and the dislocations during the film growth were evaluated. As a result, film thickness ranges with different relaxation mechanisms were classified, and dominant dislocation behavior in each phase were deduced. From the data obtained in in situ measurements, the quantitative strain relaxation models were proposed based on a dislocation kinetic model developed by Dodson and Tsao. Good agreement between the in situ data and the model ensured the validity of the dominant dislocation behavior deduced from the present study.
real-time X-Ray reciprocal space mapping during InGaAs/GaAs growth for understanding strain relaxation mechanisms佐々木 拓生*; 鈴木 秀俊*; 崔 炳久*; Lee, J.-H.*; 高橋 正光; 藤川 誠司; 新船 幸二*; 神谷 格*; 大下 祥雄*; 山口 真史*
Applied Physics Express, 2, p.085501_1 - 085501_3, 2009/07
被引用回数：35 パーセンタイル：76.10(Physics, Applied) real-time X-ray diffraction measurements during InGaAs/GaAs(001) epitaxial growth are performed for the first time to understand the strain relaxation mechanisms in a lattice-mismatched system. The high resolution reciprocal space maps of 004 diffraction obtained at interval of 6.2 nm thickness enable transient behavior of residual strain and crystal quality to be observed simultaneously as a function of InGaAs film thickness. From the evolution of these data, five thickness ranges with different relaxation processes and these transition points are determined quantitatively, and the dominant dislocation behavior in each phase is deduced.
松門 宏治*; Esirkepov, T. Z.; 木下 健一*; 大道 博行; 内海 隆行*; Li, Z.*; 福見 敦*; 林 由紀雄; 織茂 聡; 西内 満美子; et al.
Physical Review Letters, 91(21), p.215001_1 - 215001_4, 2003/11
被引用回数：137 パーセンタイル：95.16(Physics, Multidisciplinary)東京大学原子力工学研究施設の超短パルスレーザーを用いたイオン発生実験を行った。レーザーパラメーターは、波長800nm,パルス長50fs,ピーク強度6
10
W/cm
でコントラストは10
程度,ターゲットは厚さ5
mのタンタル箔を用いた。その結果、1MeVのプロトンと2MeVの電子の発生を確認した。この実験結果を解釈するために、ターゲットがプリパルスによって完全にプラズマ化した状態でメインパルスと相互作用をする低密度プラズマスラブを用いた新しいイオン加速機構を導入し、さらにそれに基づくシミュレーションを行った。実験結果とシミュレーション結果は良好な一致を示した。また、新しい加速機構が有する独自のレーザー強度に対するスケーリング側に基づいて、実用的なレーザープラズマイオン源の可能性が示される。
Khan, A.*; 山口 真史*; 大下 祥雄*; Dharmarasu, N.*; 荒木 健次*; 阿部 孝夫*; 伊藤 久義; 大島 武; 今泉 充*; 松田 純夫*
Journal of Applied Physics, 90(3), p.1170 - 1178, 2001/08
被引用回数：56 パーセンタイル：86.19(Physics, Applied)ボロン(B),ガリウム(Ga),酸素(O)炭素(C)濃度の含有量を変化させたシリコン(Si)に1MeV電子線,10MeV陽子線照射を行い、発生する欠陥をDLTS測定、キャパシタンス測定により分析した。この結果、照射によりEv-0.36eVに格子間Cと格子間Oの複合欠陥(Ci-Oi)に起因する準位が発生すること、Ec-0.18eVに格子間BとOiの複合欠陥(Bi-Oi)が生成されることが明らかになった。また、GaドープSiではCi-Oiの発生が抑制されることを見出した。Ci-Oiは再結合中心として働くことから、この抑制はSi太陽電池の耐放射線性向上につながると考えられる。また、GaドープSiではEv+0.18eVに新たな準位が形成され、この準位は350
での熱処理で消失することが判明した。
堀田 政國*; 木下 直人*; 吉岡 尚也*; 土原 久哉*
JNC TJ7400 2005-014, 424 Pages, 1997/03
本研究では、試験坑道掘削の前・中・後に、試験坑道周辺岩盤の試験坑道掘削前後の特性変化や掘削中の周辺岩盤の挙動変化を把握するための計測を実施した。
吉岡 尚也*; 土原 久哉*; 堀田 政国*; 木下 直人*
PNC TJ1449 96-007, 349 Pages, 1996/03
深部岩盤内に空洞などを構築するとき、空洞近傍の岩盤は力学的・水理学的な影響を受け、空洞内や岩盤内に様々な不安定現象をもたらすことがこれまでに経験されている。本研究の目的は釜石原位置試験第2フェーズとして、深部岩盤に位置する釜石鉱山250mレベル坑道(土被り730m)の掘削によって受ける影響領域について評価することである。対象とする岩盤は栗橋花崗閃緑岩を母岩とするき裂性岩盤である。平成7年度は試験坑道の掘削、および調査・試験のための準備として計測坑道と試錐孔の掘削を行い、予備計測(AE、Pac-Ex、振動計測)弾性波探査、室内岩石試験、および予備解析を実施した。計測坑道は普通発破工法とスムースブラスティング工法によって掘削し、発破データの収集と掘削精度を検証した。AE計測は、掘削による岩盤内のき裂発生と進展に伴うAE波を収集し、AE信号の経時的変化とその平面分布特性を把握した。また、坑道掘削時のき裂の変位とそれにともなう間隙水圧の変化とき裂の透水性の変化を測定する計測装置Pac-Ex(パッカー付き裂変位計)測定が試行され、精度のよい計測ができた。坑道掘削時に発破振動計測が試行され、加速度計の選定と設置方法に関する基礎データを得ることができた。坑道掘削終了後に坑内弾性波探査屈折法とPS検層を行い、坑道周辺岩盤の弾性波速度分布を把握した。また、坑道内の地質・き裂調査と試錐孔のコア観察、孔壁観察を行い、対象領域の地質・き裂分布特性を調査した。さらに、試錐コアを用いて室内岩石物理・力学特性試験、およびき裂特性試験を行った。平成6年度に実施されたき裂・岩石物性基いた有限要素法と個別要素法による掘削解析から、行動掘削前の対象領域における力学状況の予備的検討を行った。以上の結果から対象岩盤の発破特性の評価と試験坑道の発破パターンの設計、種々の計測・試験法の適用性評価、発破工法の違いによる弾性波速度分布の把握、岩石と単一き裂の応用・変形挙動の定量的評価を行い、さらに対象岩盤のき裂分布特性と坑道掘後の岩盤内応用・変形状態の推定ができた。
堀田 政國*; 木下 直人*; 吉岡 尚也*; 永久 和正*
JNC TJ7400 2005-013, 445 Pages, 1995/03
JNC-TJ7400-2005-013.PDF:15.85MB
釜石鉱山250mレベル坑道において、坑道および試錐孔を利用した調査・試験を実施し、既存の調査手法の有効性を検討するとともに、既存坑道周辺の掘削影響領域の特性および広がりの把握を行った。
江本 隆; 大村 明子; 山崎 良雄; 武井 早憲; 平野 耕一郎; 尾下 博教
第17回リニアック国際会議(LINAC 94), ,
現在、事業団での開発中の大電力CW(連続波)電子線形加速器は、進行波還流型(TWRR)加速器である。 本発表では全体の進捗状況を述べると共に、次の技術についてその設計思想並びに新たな試みをしている点などを述べる。 (1)低エネルギー大電力用固体ディスクビームダンプ、 (2)L-バンド大電力クライストロンパルス電源およびその励振器、 (3)高速バスで接続された加速器の計測・制御用計算機システムおよび (4)並列入出力計算機によるデーター処理装置
