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新井 太貴*; 吉越 章隆; 本橋 光也*
材料の科学と工学, 60(5), p.153 - 158, 2023/10
現在、Si酸化膜は絶縁材料として電子デバイスや生体材料に広く利用されている。この膜の原子結合状態は、各デバイスの特性に影響を与えるため、特に膜のSiとOの化学結合状態の理解と制御が必要となる。本研究では、極低濃度のHF水溶液を用いた陽極酸化によってSi基板表面に形成されるSi酸化膜をX線光電子分光によって分析した。Si2pおよびF1sスペクトルを中心に調べた。HF濃度がppmオーダであるにもかかわらず、膜表面にパーセントオーダのFを含んでいることがわかった。膜中にSi-FやSi-O-F結合が形成されたことを示唆する結果である。また、FとOの深さ分布が異なることから、FとOで表面反応プロセスが異なることが推論された。
species at SiO/Si interfaces in Si dry oxidation; Comparison between p-Si(001) and n-Si(001) surfaces津田 泰孝; 吉越 章隆; 小川 修一*; 坂本 徹哉*; 山本 善貴*; 山本 幸男*; 高桑 雄二*
Journal of Chemical Physics, 157(23), p.234705_1 - 234705_21, 2022/12
被引用回数：0 パーセンタイル：0.01(Chemistry, Physical)This paper gives experimental evidence for that (1) the excess minority carrier recombination at the SiO
/p-Si(001) and SiO/n-Si(001) interfaces is associated with the O dissociative adsorption, (2) the 700-eV X-ray induced enhancement of the SiO growth is not caused by the band flattening due to the surface photovoltaic effect but ascribed to the electron-hole pair creation due to core level photoexcitation for the spillover of the bulk Si electronic states to the SiO layer, (3) changes of band bending result from the excess minority carrier recombination at the oxidation-induced vacancy site when turning on and off the X-ray irradiation, and (4) a metastable chemisorbed O species (Pb1-paul) plays a decisive role in combining two kinds of the reaction loops of single- and double-step oxidation. Based on the experimental results, the unified Si oxidation reaction model mediated by point defect generation [Jpn. J. Appl. Phys. 59, SM0801 (2020)] is extended from a viewpoint of (a) the excess minority carrier recombination at the oxidation-induced vacancy site and (b) the trapping-mediated adsorption through the chemisorbed O species at the SiO/Si interface.
molecule at SiO/Si(001) interface during Si dry oxidation津田 泰孝; 吉越 章隆; 小川 修一*; 坂本 徹哉*; 高桑 雄二*
e-Journal of Surface Science and Nanotechnology (Internet), 21(1), p.30 - 39, 2022/11
We irradiated n-Si(001) with a 0.06 eV supersonic O molecular beam and characterized the SiO surface and SiO/Si interface using real-time X-ray photoemission spectroscopy. The molecularly-adsorbed O was observed not only during the Si surface oxidation process but also during the SiO/Si interface oxidation process, suggesting that trapping-mediated adsorption occurs at SiO/Si interface as well as on the Si surface. We found a good linear correlation between the SiO/Si interface oxidation rate and the amount of molecularly-adsorbed O, revealing that the double-step oxidation loop exclusively proceeds through P
-paul formation and minority carrier trapping at room temperature. The offset of the linear correlation indicates the presence of ins-paul on the SiO surface, which has nothing to do with the double-step oxidation loop because point defect generation is not affected by the volume expansion of ins-paul oxidation in the flexible SiO network.
高桑 雄二*; 小川 修一*; 吉越 章隆
放射光, 35(3), p.158 - 171, 2022/05
放射光を用いた大気圧光電子分光(Ambient Pressure X-ray Photoelectron Spectroscopy: APXPS)による表面反応観察は2005年頃より急速に普及し、触媒などの固相/気相界面、電池などの固相/液相界面、イオン液体などの気相/液相界面の実用的研究分野で広範囲に利用されている。本解説ではAPXPS開発の黎明期、Si気相成長とSi酸化反応キネティクスのリアルタイム観察、APXPSの課題と今後の展望について述べた。
北山 佳治; 寺阪 祐太; 佐藤 優樹; 鳥居 建男
Journal of Nuclear Engineering and Radiation Science, 7(4), p.042006_1 - 042006_7, 2021/10
Gamma-ray imaging is a technique to visualize the spatial distribution of radioactive materials. Recently, gamma-ray imaging has been applied to research on decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS) accident and environmental restoration, and active research has been conducted. This study is the elemental technology study of the new gamma-ray imager GISAS (Gamma-ray Imager using Small-Angle Scattering), which is assumed to be applied to the decommissioning site of FDNPS. GISAS consists of a set of directional gamma-ray detectors that do not require a shield. In this study, we investigated the feasibility of the shield free directional gamma-ray detector by simulation. The simulation result suggests that by measuring several keV of scattered electron energy by scatterer detector, gamma rays with ultra-small angle scattering could be selected. By using Compton scattering kinematics, a shield-free detector with directivity of about 10
could be feasible. By arranging the directional gamma-ray detectors in an array, it is expected to realize the GISAS, which is small, light, and capable of quantitative measurement.
松本 貴裕*; 杉本 秀彦*; 大原 高志; 徳光 昭夫*; 冨田 誠*; 池田 進*
Physical Review B, 103(24), p.245401_1 - 245401_9, 2021/06
被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)We investigate the quantum entangled state of two protons terminating on a silicon surface. The entangled states were detected using the surface vibrational dynamics of nanocrystalline silicon with inelastic neutron scattering spectroscopy. The protons are identical, therefore the harmonic oscillator parity constrains the spin degrees of freedom, forming strongly entangled states for all the energy levels of surface vibrations. Compared to the proton entanglement previously observed in hydrogen molecules, this entanglement is characterized by an enormous energy difference of 113 meV between the spin singlet ground state and the spin triplet excited state. We theoretically demonstrate the cascade transition of terahertz entangled photon pairs utilizing proton entanglement.
松本 貴裕*; 野又 郁実*; 大原 高志; 金光 義彦*
Physical Review Materials (Internet), 5(6), p.066003_1 - 066003_9, 2021/06
被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)The hydrogen isotope deuterium has attracted special interest for the manufacture of silicon (Si) semiconductors as well as for the synthesis of isotopically labeled compounds. However, the efficient production of D or H deuteride in a controlled manner is challenging, and rational H isotope enrichment protocols are still lacking. Here, we demonstrate a highly efficient exchange reaction from H to D on the surface of nanocrystalline Si. Fourfold enrichment of D termination was successfully achieved by dipping n-Si into a dilute D solution. By determining the surface-localized vibrational modes for H-and D-terminated n-Si using inelastic neutron scattering spectroscopy, we found that the physical mechanism responsible for this enrichment originates from the difference in the zero-point oscillation energies and entropies of the surface-localized vibrations.
森下 祐樹; Ye, Y.*; Mata, L.*; Pozzi, S. A.*; Kearfott, K. J.*
Radiation Measurements, 137, p.106428_1 - 106428_7, 2020/09
被引用回数：8 パーセンタイル：60.71(Nuclear Science & Technology)ラドン測定用のコンパクトな有機シンチレータベースの
/
検出器を開発し、ユニークで小さなラドンチャンバーを使用して特徴付けた。検出器は、シリコン貫通電極(TSV)シリコン光電子増倍管(またはSiPM)と6mm
6mm6mmのスチルベン結晶キューブで構成されている。SiPMからのアナログ信号はデジタイザに送信される。検出器は遮光ボックスに収納されており、
Rnガスが内部に拡散できるようにボックスの片側に空気ろ紙が取り付けられる。ミシガン大学の地下室に設置された検出器とAlphaGUARD検出器を使用して、
Ra線源とともに小さなラドンチャンバーに両方の検出器を配置して他の実験を行った。パルス形状識別手法を適用することにより、アルファスペクトルとベータスペクトルを同時にかつ明確に分離し、それらを定量的に測定することができた。測定されたアルファスペクトルに2つのピークが検出され、
Poによる低エネルギーピークと
Poによる高エネルギーピークであった。AlphaGUARDのラドン濃度と/検出器の計数率との間の線形関係が確認された。/検出器の厚さは10mm未満であった。したがって、このコンパクトな有機シンチレータベースの/検出器は、新しいラドン検出システムとして有用となる可能性がある。
小川 修一*; 吉越 章隆; Tang, J.*; 堰端 勇樹*; 高桑 雄二*
Japanese Journal of Applied Physics, 59(SM), p.SM0801_1 - SM0801_42, 2020/07
被引用回数：5 パーセンタイル：33.01(Physics, Applied)この論文では、SiO/Si界面付近の点欠陥生成を介したSi酸化反応の統一モデルに関するレビューをする。この点欠陥は放出されたSi原子と空孔からなり、このダングリングボンドにおいてO分子の解離吸着が起きる。点欠陥の生成速度が、酸化にともない誘起される歪み、SiとSiO間の熱膨張係数の違いに起因する熱歪み、熱励起によるSi放出の速度および吸着熱の組み合わせによって与えられることを示す。
2) investigated using supersonic seeded molecular beams大野 真也*; 田中 一馬*; 小玉 開*; 田中 正俊*; 吉越 章隆; 寺岡 有殿*
Surface Science, 697, p.121600_1 - 121600_6, 2020/07
被引用回数：1 パーセンタイル：6.04(Chemistry, Physical)放射光高分解能光電子分光法によってシリコン(113)表面の初期酸化を調べた。本研究では、Si2pとO1s光電子スペクトルから酸化物の厚さおよび組成を評価するとともにSiO/Si界面のひずみを評価した。Si2pから酸化成分(Si
, Si
, Si
, Si
)を分析した。また、O1sスペクトルは、低結合エネルギー成分(LBC)および高結合エネルギー成分(HBC)に分離された。非熱酸化プロセスを調べるために、並進運動エネルギー(
)を高めることが可能な超音速シード分子ビーム(SSMB)を使った。酸化物の品質と酸化速度が、を変えることで大きく変わることが明らかになった。
玉熊 佑紀*; 山田 椋平; 岩岡 和輝*; 細田 正洋*; 黒木 智広*; 水野 裕元*; 山田 宏治*; 古川 雅英*; 床次 眞司*
Perspectives in Science (Internet), 12, p.100414_1 - 100414_4, 2019/09
緊急時において放射性プルーム(例えば、
I, 
Cs及び
Cs)を検知するために、シリコンフォトダイオードを用いた可搬型の放射性プルームモニタを開発した。バックグラウンド計数率は周辺線量当量率に比例し、ISO11929に従って算出した周辺線量当量率20
Sv h
下におけるモニタの検出限界は187Bq m
であった。これらの結果は、最適な厚さを有する鉛遮蔽体によってシステムの検出限界を効果的に低減することができることを示唆している。
冠城 雅晃; 佐藤 優樹; 吉原 有里*; 島添 健次*; 高橋 浩之*; 鳥居 建男
Reactor Dosimetry; 16th International Symposium on Reactor Dosimetry (ISRD-16) (ASTM STP 1608), p.405 - 414, 2018/11
被引用回数：0 パーセンタイル：0.05(Nuclear Science & Technology)On March 11, 2011, a massive earthquake occurred in the Tohoku region of Japan, and a large tsunami hit the Fukushima Daiichi Nuclear Power Plant (1F), resulting in a nuclear accident. Despite the years that have passed since the accident, decommissioning remains a concern. Radiation measurement techniques are very important for accelerating the decommissioning and ensuring low radiation exposure to workers. Our gamma-ray imaging system is the detection device for determining the three dimensional radioactive distributions of nuclear fuel debris, measuring high-energy gamma rays (greater than 1 MeV). Silicon semiconductor detectors are among the candidate detectors for radiation measurements in our system because of their radiation-hardness and high counting rate capability. We have been developing a stacked amorphous-silicon (Si)/crystal-Si heterojunction Si strip detector, which has 1-mm-pitch striped electrodes (0.5 mm wide) and 1.2-mm-pitch stacked technology. The detector consists of an Si strip mounted on a thin printed circuit board, front-end readout electronics with a complementary metal oxide semiconductor application specific integrated circuit, and a field programmable gate array. The threshold level of energy deposition of each pulse signal in each channel can be set from the application-specific integrated circuit, and gamma-ray images with energy discrimination can be obtained. The energy threshold level for discrimination of 
Co gamma rays from Cs gamma rays was investigated experimentally and by means of simulation, and it was found to be about 500 keV. Therefore, our Si strip detector has the required position sensitivity and energy discrimination ability for identifying high-energy gamma-ray source distributions.
松本 貴裕*; 大原 高志; 杉本 秀彦*; Bennington, S. M.*; 池田 進*
Physical Review Materials (Internet), 1(5), p.051601_1 - 051601_6, 2017/10
被引用回数：2 パーセンタイル：7.76(Materials Science, Multidisciplinary)We identified twin split scattering spectra in hydrogen-terminated nanocrystalline silicon by using inelastic neutron scattering spectroscopy. A standard theoretical analysis based on the localized wave function of hydrogen in not sufficient to explain this duality. We show that this duality originates from the cooperative motion of hydrogen and silicon.
下山 巖; 馬場 祐治; 平尾 法恵*
Applied Surface Science, 405, p.255 - 266, 2017/05
被引用回数：1 パーセンタイル：5.94(Chemistry, Physical)イオンビームによりヘテロ原子ドーピングを行ったグラファイト基板上に蒸着したポリジメチルシラン(PDMS)薄膜の配向構造を調べるため、吸収端近傍X線吸収微細構造(NEXAFS)分光法を用いた。Si 
端NEXAFSスペクトルは非照射基板上とN
照射基板上で互いに逆の傾向を示す偏光依存性を示し、Arイオン照射基板上では偏光依存性を示さなかった。第一原理計算によるNEXAFSスペクトルの理論的解釈に基づき、PDMSは非照射基板で水平配向、N照射基板上で垂直配向、Ar+イオン照射基板上でランダム配向をとることがわかった。我々はさらに光電子顕微鏡を用いた分析を行い、同一基板上で照射・非照射領域が分離した表面でPDMS薄膜がmオーダーで異なる配向を持ちうることを見いだした。これらの結果は集光イオンビームを用いたグラファイトの表面改質が有機薄膜のための新たな微細配向制御法となる可能性を示唆している。
Thalmeier, R.*; 谷田 聖; 他97名*
Nuclear Instruments and Methods in Physics Research A, 845, p.633 - 638, 2017/02
被引用回数：6 パーセンタイル：51.46(Instruments & Instrumentation)The Belle II Experiment at the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, will explore the asymmetry between matter and antimatter and search for new physics beyond the standard model. 172 double-sided silicon strip detectors are arranged cylindrically in four layers around the collision point to be part of a system which measures the tracks of the collision products of electrons and positrons. A total of 1748 radiation-hard APV25 chips read out 128 silicon strips each and send the analog signals by time-division multiplexing out of the radiation zone to 48 Flash Analog Digital Converter Modules (FADC). Each of them applies processing to the data; for example, it uses a digital finite impulse response filter to compensate line signal distortions, and it extracts the peak timing and amplitude from a set of several data points for each hit, using a neural network. We present an overview of the SVD data readout system, along with front-end electronics, cabling, power supplies and data processing.
Adamczyk, K.*; 谷田 聖; Belle-II SVD Collaboration*; 他97名*
Nuclear Instruments and Methods in Physics Research A, 845, p.38 - 42, 2017/02
被引用回数：0 パーセンタイル：0.02(Instruments & Instrumentation)The Belle II experiment at the asymmetric SuperKEKB collider in Japan will operate at an instantaneous luminosity approximately 50 times greater than its predecessor (Belle). The central feature of the experiment is a vertex detector comprising two layers of pixelated silicon detectors (PXD) and four layers of double-sided silicon microstrip detectors (SVD). One of the key measurements for Belle II is CP violation asymmetry in the decays of beauty and charm hadrons, which hinges on a precise charged-track vertex determination and low-momentum track measurement. Towards this goal, a proper assembly of the SVD components with precise alignment ought to be performed and the geometrical tolerances should be checked to fall within the design limits. We present an overview of the assembly procedure that is being followed, which includes the precision gluing of the SVD module components, wire-bonding of the various electrical components, and precision 3D coordinate measurements of the final SVD modules.
Kang, K. H.*; 谷田 聖; Belle-II SVD Collaboration*; 他94名*
Nuclear Instruments and Methods in Physics Research A, 831, p.213 - 220, 2016/09
被引用回数：0 パーセンタイル：0.02(Instruments & Instrumentation)A silicon vertex detector (SVD) for the Belle-II experiment comprises four layers of double-sided silicon strip detectors (DSSDs), assembled in a ladder-like structure. Each ladder module of the outermost SVD layer has four rectangular and one trapezoidal DSSDs supported by two carbon-fiber ribs. In order to achieve a good signal-to-noise ratio and minimize material budget, a novel chip-on-sensor "Origami" method has been employed for the three rectangular sensors that are sandwiched between the backward rectangular and forward (slanted) trapezoidal sensors. This paper describes the bonding procedures developed for making electrical connections between sensors and signal fan-out flex circuits (i.e., pitch adapters), and between pitch adapters and readout chips as well as the results in terms of the achieved bonding quality and pull force.
Adamczyk, K.*; 谷田 聖; 他94名*
Nuclear Instruments and Methods in Physics Research A, 824, p.381 - 383, 2016/07
被引用回数：0 パーセンタイル：0.02(Instruments & Instrumentation)The Belle II experiment at the SuperKEKB asymmetric 
collider in Japan will operate at a luminosity approximately 50 times larger than its predecessor (Belle). At its heart lies a six-layer vertex detector comprising two layers of pixelated silicon detectors (PXD) and four layers of double-sided silicon microstrip detectors (SVD). One of the key measurements for Belle II is time-dependent CP violation asymmetry, which hinges on a precise charged-track vertex determination. Towards this goal, a proper assembly of the SVD components with precise alignment ought to be performed and the geometrical tolerances should be checked to fall within the design limits. We present an overview of the assembly procedure that is being followed, which includes the precision gluing of the SVD module components, wire-bonding of the various electrical components, and precision three dimensional coordinate measurements of the jigs used in assembly as well as of the final SVD modules.
Adamczyk, K.*; 谷田 聖; 他94名*
Nuclear Instruments and Methods in Physics Research A, 824, p.406 - 410, 2016/07
被引用回数：6 パーセンタイル：49.29(Instruments & Instrumentation)The silicon vertex detector of the Belle II experiment, structured in a lantern shape, consists of four layers of ladders, fabricated from two to five silicon sensors. The APV25 readout ASIC chips are mounted on one side of the ladder to minimize the signal path for reducing the capacitive noise; signals from the sensor backside are transmitted to the chip by bent flexible fan-out circuits. The ladder is assembled using several dedicated jigs. Sensor motion on the jig is minimized by vacuum chucking. The gluing procedure provides such a rigid foundation that later leads to the desired wire bonding performance. The full ladder with electrically functional sensors is consistently completed with a fully developed assembly procedure, and its sensor offsets from the design values are found to be less than 200 m. The potential functionality of the ladder is also demonstrated by the radioactive source test.
Adamczyk, K.*; 谷田 聖; 他94名*
Nuclear Instruments and Methods in Physics Research A, 824, p.480 - 482, 2016/07
被引用回数：1 パーセンタイル：11.14(Instruments & Instrumentation)The Belle-II VerteX Detector (VXD) has been designed to improve the performances with respect to Belle and to cope with an unprecedented luminosity of 810
cm
s achievable by the SuperKEKB. Special care is needed to monitor both the radiation dose accumulated throughout the life of the experiment and the instantaneous radiation rate, in order to be able to promptly react to sudden spikes for the purpose of protecting the detectors. A radiation monitoring and beam abort system based on single-crystal diamond sensors is now under an active development for the VXD. The sensors will be placed in several key positions in the vicinity of the interaction region. The severe space limitations require a challenging remote readout of the sensors.
