Country：Japan

Award type：Award from publisher, newspaper, foundation, etc.  Country：Japan

Country：Japan

Language：English   Publishing type：Research paper (scientific journal)  

A novel full-field X-ray fluorescence microscope based on total-reflection advanced Kirkpatrick–Baez mirror optics was developed. The total-reflection imaging mirror optics arrangement, with four reflections, has the advantage of being able to function both as a powerful low-pass energy filter, completely rejecting incident excitation X-rays, and as an achromatic optical imaging system. Isolated X-ray fluorescence signals can be imaged, avoiding imaging-detector saturation, with low background noise. A prototype fluorescence microscope constructed at SPring-8 demonstrated the capability to simultaneously image elemental distributions using various X-ray fluorescence signals (Ni, Cu, Zn, Ge, and Bi). A half-period spatial resolution of ~0.5–1 µm (1000–500 LP/mm) was achieved, owing to the achromaticity of the imaging mirrors and the photon-counting scheme of the CCD camera used for fluorescence detection.

DOI： 10.1364/OE.27.018318

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrated that the combination of a hyperbolic convex and elliptical concave mirrors works as a compact reflective X-ray imaging system with a short optical focal length and large magnification factor. We performed an experiment to form a one-dimensional demagnified image with a demagnification factor of 321 within an approximately 2-m-long optical setup at an X-ray energy of 10 keV. The results showed that this imaging optics system is capable of providing a resolution of ~40 nm. From wavefront analysis, it was confirmed that the optics possessed a wide field-of-view with a significant reduction of comatic aberration.

DOI： 10.1364/oe.27.003429

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

A method of fabricating multilayer focusing mirrors that can focus X-rays down to 10 nm or less was established in this study. The wavefront aberration induced by multilayer Kirkpatrick-Baez mirror optics was measured using a single grating interferometer at a photon energy of 9.1 keV at SPring-8 Angstrom Compact Free Electron Laser (SACLA), and the mirror shape was then directly corrected by employing a differential deposition method. The accuracies of these processes were carefully investigated, considering the accuracy required for diffraction-limited focusing. The wavefront produced by the corrected multilayer focusing mirrors was characterized again in the same manner, revealing that the root mean square of the wavefront aberration was improved from 2.7 (3.3) rad to 0.52 (0.82) rad in the vertical (horizontal) direction. A wave-optical simulator indicated that these wavefront-corrected multilayer focusing mirrors are capable of achieving sub-10-nm X-ray focusing.

DOI： 10.1038/s41598-018-35611-0

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Antiviral Research  

HIV-associated lipodystrophy has been reported in people taking anti-retroviral therapy (ART). Lipodystrophy can cause cardiovascular diseases, affecting the quality of life of HIV-infected individuals. In this study, we propose a pharmacological lipid index to estimate the risk of hyperlipidemia caused by anti-retroviral drugs. Lipid droplets were stained in cells treated with anti-retroviral drugs and cyclosporin A. Signal intensities of lipid droplets were plotted against the drug concentrations to obtain an isodose of 10 μM of cyclosporin A, which we call the Pharmacological Lipid Index (PLI). The PLI was then normalized by EC50. PLI/EC50 values were low in early proteinase inhibitors and the nucleoside reverse transcriptase inhibitor, d4T, indicating high risk of hyperlipidemia, which is consistent with previous findings of hyperlipidemia. In contrast, there are few reports of hyperlipidemia for drugs with high PLI/EC50 scores. Data suggests that PLI/EC50 is a useful index for estimating the risk of hyperlipidemia.

DOI： 10.1016/j.antiviral.2024.105819

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PubMed

Language：English  

DOI： 10.21203/rs.3.rs-3384984/v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/PhysRevLett.131.163201

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PubMed

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.131.163201/fulltext

Authorship：Last author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：公益社団法人 精密工学会  

<p>X線ビームサイズを制御できる光学システムは未だ実用化されておらず，高精度な形状可変ミラーが注目されている．これまでにニオブ酸リチウム（LN）を用いた高安定なミラーを開発したが，圧電定数が小さいため，このままではビームサイズの大幅な変化は見込めない．これを解決するために，LNの分極反転特性を活かしたバイモルフミラーを開発した．本発表では，X線波面計測法に基づき変形性能を評価した結果について報告する． </p>

DOI： 10.11522/pscjspe.2023a.0_572

CiNii Research

Authorship：Last author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：公益社団法人 精密工学会  

<p>Advanced Kirkpatrick-Baezミラーを用いた結像型X線顕微鏡は，高空間分解能な観察を高効率かつ色収差なく行えるという利点を持つ．一方で，アライメントの難易度やミラーに要求される形状精度が高く，未知のアライメント誤差及びミラー形状誤差により生じる光学収差が更なる高空間分解能化を律速させている．本講演では，試料を面内回転させることで未知の光学収差を分離可能な新規手法を提案する．</p>

DOI： 10.11522/pscjspe.2023a.0_579

CiNii Research

Authorship：Last author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：公益社団法人 精密工学会  

<p>結像型X線顕微鏡の超高空間分解能5nmを達成するためには，1nm PV以上の形状精度を満たすX線ミラーが必要である．しかし，その精度は現代の加工技術では達成不可能である．この問題を解決するため，単結晶圧電素子であるニオブ酸リチウムを利用した形状可変ミラーに基づくアダプティブ結像型X線顕微鏡を開発している．本発表では，開発した補償光学系を構築し，SPring-8にて実証実験を行った結果について報告する．</p>

DOI： 10.11522/pscjspe.2023a.0_576

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41598-023-30498-y

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PubMed

Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>ミラーを用いた結像型X線顕微鏡は色収差がなく、効率も高いといった特徴を持っている。一方でミラーの製作難度は非常に高く、技術的観点からさらなる高分解能化は非常に難しい。そこで我々は、合成開口および光学収差の分離による分解能向上を見込めるフーリエタイコグラフィに着目した。ミラーを用いたX線顕微鏡像にこれを適用することで、結像システムの回折限界を超える空間分解能で試料像を得ることを試みた。</p>

DOI： 10.11522/pscjspe.2023s.0_680

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>ミラーベースの結像型X線顕微鏡は優れた性能を有しており，更なる高分解能化が期待されている．そのためには，高精度なミラーが不可欠だが，もはや現行の加工技術では満足できない．この問題を解決するために，ニオブ酸リチウム（ＬＮ）製の形状可変ミラーを開発している．本発表では，変形可能な空間周波数を更に向上させるために開発した，複数枚のＬＮを積層させた新規構造ミラーについて報告する．</p>

DOI： 10.11522/pscjspe.2023s.0_683

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>X線複合分析を実現するために，X線ビームサイズを変えられる光学システムが求められており，形状可変ミラーが注目されている．これまでにニオブ酸リチウム（LN）を用いた高安定なミラーを実現した．一方で，変形量が小さいため，ビームサイズを大きく変えることができない．この問題を解決するために，LNの分極反転特性に着目した．本発表では，約1100℃でアニールしたLNミラーの基礎検討結果を報告する．</p>

DOI： 10.11522/pscjspe.2023s.0_684

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>我々は硬X線FELにおける10²² W/cm²強度の達成のために sub-10 nm集光光学系を開発している．極微小な集光径評価のためには，デフォーカス位置におけるタイコグラフィ法が適用可能であるが，低次波面収差と照射位置誤差がどちらも存在する場合に，誤った解に収束することが問題となっていた．本研究では，複数のデフォーカス位置での計測手法・再構成アルゴリズムを新たに開発し，SACLA BL3にて実証実験を行った結果について報告する．</p>

DOI： 10.11522/pscjspe.2023s.0_678

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>ミラーベースX線顕微鏡の更なる高分解能化のためには，ミラーの高精度化が求められるが，加工技術の限界が近づいている．これを解決するために，形状可変ミラーとin-situ波面計測法を組み合わせたアダプティブ顕微鏡の開発を進めている．フレネルゾーンプレートの集光点を用いた波面計測法と，その応用であるテストチャートのエッジの回折光を用いた波面計測法を提案し，その実証実験を行った．</p>

DOI： 10.11522/pscjspe.2023s.0_687

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.89.147

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.89.157

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>超高分解能なアダプティブX線顕微鏡の実現を目指し，顕微鏡上にてin-situでの波面計測を行う技術の開発を進めた．機械学習を用いて既知試料の顕微鏡像から波面を推定する手法を提案した．計算と実験のそれぞれで得た二種類の顕微鏡像を機械学習の入力とし用い，本手法の実現可能性を検証した．この結果，両者とも推定波面から再現した顕微鏡像とインプットした顕微鏡像がよく一致し，本手法の有効性を示すことができた．</p>

DOI： 10.11522/pscjspe.2022a.0_74

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>形状可変ミラーを用いたアダプティブ波面修正により，超高分解能な結像型X線顕微鏡の実現に挑戦している．そのためには，拡大結像配置のままin-situにＸ線波面を計測できる手法が必要であるが，未だその手法は確立されていない．本研究ではフーリエタイコグラフィに基づいた波面計測法を提案し，本手法により拡大結像配置において高精度なin-situ X線波面計測が可能であることを実証した．</p>

DOI： 10.11522/pscjspe.2022a.0_73

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>空間分解能5nmを持つX線顕微鏡の達成には，1nm以上の形状精度を有するX線ミラーが必要である．そこで我々はニオブ酸リチウムを用いた形状可変ミラーを開発した．単結晶圧電体であるため，逆圧電効果により高精度に変形できるだけでなく，高い安定性とヒステリシスフリーを実現できる．本発表では楕円凹面の形状可変ミラーを組み込んだアダプティブAdvanced KBミラー光学系を構築し，SPring-8にてX線波面補償を行った結果について報告する．</p>

DOI： 10.11522/pscjspe.2022a.0_72

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41598-022-13377-w

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0092976

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Scopus

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>ミラーベースの結像型Ｘ線顕微鏡はスループットや色収差の点で優れているが，高空間分解能観察を行う上ではミラーの許容形状誤差が小さくなる．修正すべき形状誤差を波面に基づき計測する手法の開発が求められていたが，現行の手法では大開口ミラー全体の波面が計測できなかった．そこで本研究ではミラーの異なる位置の波面を求め，スティッチングする手法を提案した．概念実証実験によりミラー全体の波面は矛盾なく求められた．</p>

DOI： 10.11522/pscjspe.2022s.0_119

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>結像型X線顕微鏡上でin-situに波面計測を行う技術が実現すれば，アダプティブX線顕微鏡によるさらなる高分解能化が可能である．本研究では，機械学習により顕微鏡から得られた画像から波面を推定する手法の開発を行った.情報量の多いコヒーレント結像の画像を用いて,顕微鏡画像と波面のゼルニケ係数との関係を学習させた．学習済みモデルは顕微鏡画像のみからゼルニケ係数を予想することができた．</p>

DOI： 10.11522/pscjspe.2022s.0_114

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>高分解能な結像型X線顕微鏡を実現するためには、より高精度な光学素子が必要となる。しかし、光学素子の作製精度は限界に達しており、この問題解決のため形状可変ミラーの導入を進めている。これまでの形状可変ミラーは、高空間周波数の形状が制御不能、圧電素子由来の不安定性などの欠点を有する。そこで、本研究では単結晶圧電素子を用いた新構造の形状可変ミラーを提案、試作し、性能評価を実施した。</p>

DOI： 10.11522/pscjspe.2022s.0_116

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>X線領域では、高精度な光学素子が必要とされる。しかし、その作成難易度は限界(1nm)に到達しつつあり、これら光学素子によって乱された波面を形状可変ミラーによって修正する戦略が今後重要となる。本研究では、単結晶圧電素子であるニオブ酸リチウムを用いた極シンプルな形状可変ミラーを試作した。SPring-8にてＸ線波面計測を試みたところ、試作した形状可変ミラーが意図したとおり変形できることを確認した。</p>

DOI： 10.11522/pscjspe.2022s.0_661

CiNii Research

Language：English   Publisher：European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022  

In recent years, crystalline silicon (Si) has been used as a promising material for precision X-ray mirrors and Bragg optics. These devices require extremely well-ordered surfaces without crystallographic damage. Thus, we applied an ultra-precision polishing method called catalyst-referred etching (CARE) to planarize crystalline Si substrates. CARE is a catalyzed chemical etching method that uses pure water as an etchant and a catalytic pad that promotes the designed reactions. Owing to its abrasive-free nature, the polished surface reaches an atomic-level smoothness suitable for application to excellent optical devices, particularly in the X-ray regime. Understanding the mechanism of this method is essential for its wide practical application. CARE has been successfully applied to silicon dioxide (SiO2) optical glasses, and the removal mechanism has been clarified to be an indirect hydrolysis reaction using first-principles calculations. In the case of Si CARE, because Si is easily oxidized by dissolved oxygen (DO) in pure water, the removal pathway may involve oxidation reactions, which may be similar to the removal mechanism of SiO2CARE. Clarifying the role of DO is essential for understanding the mechanism of Si CARE. In this study, we evaluated the processing characteristics under different DO concentrations and investigated whether the accompanying oxidation induced by DO is critically required. It was observed that Si CARE does not require oxidation. The surface roughness was observed to be drastically improved in low-DO water. We conclude that the etching mechanism of Si CARE is different from that of SiO2CARE. Thus, a first-principles investigation is possible, except for the O2molecule from relevant reactions.

Scopus

Language：English   Publisher：European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022  

In recent years, polymer materials with excellent properties, such as chemical resistance, heat resistance, and high insulation, have been produced. These materials have been widely used in advanced devices. For example, polycarbonate (PC), polymethyl methacrylate (PMMA), and polyimide (PI) are used as insulating films in microelectromechanical systems (MEMSs), and polytetrafluoroethylene (PTFE) is a promising substrate for next-generation high-frequency devices exceeding 5G. To exploit the excellent properties of these polymer materials, well-ordered surfaces are required. However, because polymer materials are extremely soft, conventional polishing methods that use abrasives cannot produce a damage-free surface. We present an abrasive-free polishing technique called catalyst-referred etching (CARE). In this method, the top surface of the workpiece is preferentially removed via an indirect hydrolysis reaction promoted by a metal catalyst. The surfaces of the amorphous and single-crystalline samples processed using CARE exhibited atomic flatness. We discuss the polishing characteristics and material removal mechanisms of polymers in CARE. The PC and PMMA were polished using Pt and pure water as the catalyst and etchant, respectively. An atomically smooth surface, which could not be fabricated by mechanical polishing, was obtained. Based on observations of the surface, the removal mechanism was estimated as follows. Molecule chains entangle to form clusters that constitute the surface of the polymer and determine the surface roughness. In CARE, the top of this cluster was selectively removed, forming a flat surface similar to that obtained on a single-crystalline polymer material. Therefore, CARE is a promising polishing method for polymer materials.

Scopus

Language：English   Publisher：European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022  

Recently, polycrystalline material can express its excellent physical properties and has been used in advanced applications in semiconductors and optics. Similar to single crystal materials, to fully exploit the properties of polycrystalline material in devices, a flat surface on the atomic level is required. However, since the polycrystalline material surface has various crystal orientations, the grain boundary steps appear on the surface polished by CMP (chemical mechanical polishing). Thus, new polishing technology needs to be developed. The following two conditions are required to obtain atomically well-ordered polycrystalline material surfaces: 1) The polishing pad must always act as a reference flat to selectively remove the crystal grain located at the topmost of the sample surface. 2) The material removal must proceed via a chemical etching to avoid crystallographic damages. Therefore, we developed a chemical etching method assisted by a metal catalyst named catalyst-referred etching (CARE). In this method, a polishing pad with a catalyst thin film works as a reference plane to be copied onto the workpiece surface. A workpiece is pressed to the polishing pad in an etchant, and they rotate around their axes. Accordingly, only the grain located at the topmost site frequently contacts the catalyst and is preferentially removed chemically, leading to obtaining a damage-free surface without grain boundary steps. In this study, we demonstrated the possibility of realizing the atomically flat polycrystalline surface by applying the CARE. Polycrystalline SiC and YAG ceramics were processed using Ru catalyst and a solution having neutral pH as a catalyst and an etchant, respectively. Using this method, we obtained an extremely smooth surface with a grain boundary step less than 1 nm without introducing crystallographic damage.

Scopus

Language：English   Publisher：Optics InfoBase Conference Papers  

A sub-10 nm focusing mirror system for the XFEL has been developed to generate an ultra-intense X-ray laser field. For the sub-10 nm focusing optic, an advanced Kirkpatrick-Baez mirror system based on Wolter-type III geometry has been adopted. The mirrors were fabricated based on a strategy of X-ray wavefront correction. As the results of the performance test at SACLA, we confirmed nearly diffraction-limited wavefront accuracy, 7 nm focusing spot size, more than 10 hours stability, and ~1022 W/cm2 intensity.

DOI： 10.1364/CLEOPR.2022.CWP19B_01

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

DOI： 10.1063/5.0071623

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

DOI： 10.1063/5.0070465

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PubMed

Other Link： https://aip.scitation.org/doi/pdf/10.1063/5.0070465

Language：Japanese   Publisher：The Japan Society for Precision Engineering  

We propose the using of catalyst referred etching (CARE) method to realize well-ordered surface on the polycrystalline. In CARE, the metal catalyst layer on the polishing pad works as a reference plane and only the top most site of sample surface contacted with the catalyst removed chemically. By using this processing characteristic, it is possible to obtain an ultra-smooth surface even on the polycrystalline surface having a random crystal orientation. In this experiment, we prepared polycrystalline SiC and YAG ceramics as a sample and applied CARE using Pt and pure water as a catalyst and an etchant respectivelly. As a result, an atomically smooth surface with no grain boundary steps was realized.

DOI： 10.11522/pscjspe.2021a.0_115

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>結像型X 線顕微鏡では，試料の高空間分解能な像がリアルタイムに得られる．しかし，本顕微鏡では，コントラストの低い吸収コントラスト像しか直接観察できないことから，高いコントラストを持つ位相コントラスト像の獲得が望まれる．本研究では，様々なデフォーカス位置における試料の吸収コントラスト像を用いて，位相コントラスト像を得る手法を提案した． SPring-8 BL29XUでの実験を通して本手法の有用性を実証した．</p>

DOI： 10.11522/pscjspe.2021a.0_546

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>大型放射光施設が発振する高強度X線をより小さく集光することで，高光子密度を活かしたX線非線形光学や，小さなスポット径を利用したナノ構造解析の発展が期待される．求める集光径が小さくなるほどミラーに必要な形状精度は厳しくなる．そこで我々は中周期以上の形状を形状可変ミラーで，短周期形状を差分成膜法で修正するハイブリッド波面補償を導入した．本システムを用いることで，回折限界集光条件を満たすことに成功した．</p>

DOI： 10.11522/pscjspe.2021a.0_545

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Union of Crystallography (IUCr)  

X-ray scientists are continually striving to improve the quality of X-ray microscopy, due to the fact that the information obtained from X-ray microscopy of materials can be complementary to that obtained from optical and electron microscopes. In contrast to the ease with which one can deflect electron beams, the relative difficulty to deflect X-ray has constrained the development of scanning X-ray microscopes (SXMs) based on a scan of an X-ray small probe. This restriction has caused severe complications that hinder progress toward achieving ultimate resolution. Here, a simple and innovative method for constructing an SXM equipped with a nanoprobe scanner is proposed. The nanoprobe scanner combines X-ray prisms and advanced Kirkpatrick–Baez focusing mirrors. By rotating the prisms on the order of degrees, X-ray probe scanning with single-nanometre accuracy can be easily achieved. The validity of the concept was verified by acquiring an SXM image of a test pattern at a photon energy of 10 keV, where 50 nm line-and-space structures were resolved. This method is readily applicable to an SXM with a single-nanometre resolution and will assist effective utilization of increasing brightness of fourth-generation synchrotron radiation sources.

DOI： 10.1107/S2052252521007004

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PubMed

Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.87.7_618

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>大型放射光施設が発振する高強度X線をより小さく集光することで，高光子密度を活かしたX線非線形光学や，小さなスポット径を利用したナノ構造解析の発展が期待される．求める集光径が小さくなるほどミラーに必要な形状精度は厳しくなる．そこで我々は形状可変ミラーを導入し，有限要素法を用いて修正可能な形状を計算した．6周期までの正弦波型の初期形状誤差がPV-3 nm以上存在した場合においても修正可能であることがわかった．</p>

DOI： 10.11522/pscjspe.2021s.0_668

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>4枚のミラーから成るAdvanced Kirkpatrick-Baezミラーは硬X線領域における有望な結像光学系である．我々は様々な光学系を実際に開発し，30nmの空間分解能を持つX線顕微鏡をすでに実現した．この光学系に複数の凸面鏡を組み入れることで，さらに高度な光学系が構築可能であることを見出した．本発表では，いくつかの設計例とシミュレーションを示し，結像特性について調査した結果を示す．</p>

DOI： 10.11522/pscjspe.2021s.0_672

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>X線ミラーを用いた結像型X線顕微鏡は，色収差が無くスループットが高い点で優れているが，許容アライメント誤差が厳しく，高空間分解能画像を得るためには，拡大結像配置にて光学素子由来の波面収差を計測しなければならない．我々は，フレネルゾーンプレートの集光点を試料とし，その拡大像を複数枚取得した上で反復的位相回復計算を施すことで波面を計測した．本手法を用いてアライメントを調整し，空間分解能23 nmを達成した．</p>

DOI： 10.11522/pscjspe.2021s.0_671

CiNii Research

Publishing type：Research paper (scientific journal)  

Semiconductor silicon carbide (SiC) is proposed to be a promising material for power-saving devices. However, due to its hard and brittle properties, there is a need to develop a highly efficient strain-free thinning process for the backside thinning of vertical power transistors. As a method for thinning SiC wafers without crystallographic damages, plasma etching with high-pressure SF6 plasma was proposed and the dependence of different processing parameters on the removal rate was investigated. The results revealed that the removal rate was mainly influenced by the power density and relatively insensitive to processing parameters such as processing gap and gas flow rate. It was discovered that a high-speed etching of the entire surface of a commercially available 2- inch wafer at approximately 15 μm min-1 can be achieved by increasing the radio frequency power. Additionally, it was demonstrated that the thickness of the 2-inch wafer can be thinned to approximately 100 μm by only 20 min plasma etching.

DOI： 10.1149/2162-8777/abdc47

Scopus

Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2562077

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

X-ray single-grating interferometry was applied to conduct accurate wavefront corrections for hard X-ray nanofocusing mirrors. Systematic errors in the interferometer, originating from a grating, a detector, and alignment errors of the components, were carefully examined. Based on the measured wavefront errors, the mirror shapes were directly corrected using a differential deposition technique. The corrected X-ray focusing mirrors with a numerical aperture of 0.01 attained two-dimensionally diffraction-limited performance. The results of the correction indicate that the uncertainty of the wavefront measurement was less than λ/72 in root-mean-square value.

DOI： 10.3390/s20247356

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1107/S1600577520008607

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Union of Crystallography (IUCr)  

This paper proposes and demonstrates a simple method using the intensity correlation of X-ray fluorescence to evaluate the focused beam size of an X-ray free-electron laser (XFEL). This method was applied to the sub-micrometre focused XFEL beam at the SPring-8 Angstrom Compact Free Electron Laser, and the beam size evaluated using the proposed method was consistent with that measured using the knife-edge scan method. The proposed method is readily applicable to extremely small X-ray spots and can be applied for the precise diagnostics of sub-10 nm focused X-ray beams which have recently emerged.

DOI： 10.1107/s1600577520009868

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Optical Society  

DOI： 10.1364/oe.398590

PubMed

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Optical Society  

DOI： 10.1364/optica.386012

Other Link： https://www.osapublishing.org/viewmedia.cfm?URI=optica-7-4-367&seq=0

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5141381

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

© 2020 by the authors. We developed an experimental platform for combinative use of an X-ray free electron laser (XFEL) and a high-power nanosecond laser. The main target of the platform is an investigation of matter under high-pressure states produced by a laser-shock compression. In this paper, we show details of the experimental platform, including XFEL parameters and the focusing optics, the laser irradiation system and X-ray diagnostics. As a demonstration of the high-power laser-pump XFEL-probe experiment, we performed an X-ray diffraction measurement. An in-situ single-shot X-ray diffraction pattern expands to a large angle side, which shows a corundum was compressed by laser irradiation.

DOI： 10.3390/app10072224

Scopus

Publishing type：Part of collection (book)  

The development of high-precision x-ray mirrors is described. Atomistic surface polishing technique, elastic emission machining (EEM), was developed more than 30 years ago. This chapter describes how the polishing technique was improved to successfully apply to the synchrotron radiation and XFEL mirrors. The key was actually the figure metrology. The metrology was dramatically advanced by using coherent x-rays at the 1-km beamline of SPring-8, where classical ray-tracing approach was no more valid so that wave-optical approach was developed. Various optical references were developed to improve the global surface figures of mirrors. Successful development of elliptical mirrors helped attaining less than 100 nm focal spot in the conventional beamlines using Kirkpatrick-Baez focusing configuration, reaching 7 nm at the 1-km beamline. The speckle-free mirrors and focusing mirrors were used in XFEL facilities. These mirrors have been applied for various types of scanning nano-probes, imaging system, and generation of high-intensity photon fields for nonlinear xray optical experiments.

DOI： 10.1007/978-3-030-23201-6_54

Scopus

Publishing type：Research paper (international conference proceedings)  

A catalytically assisted etching method was applied to planarization of Si surfaces for the ultra-precision fabrication of X-ray mirrors. The study demonstrates that an atomically smooth surface with less than 0.1 nm root-mean-square roughness could be achieved on a Si substrate using a thin metal film and pure water as the catalyst and etching solution, respectively. The removal rate using a Pt catalyst can reach to over 500 nm/h. Density functional theory calculations is carried out to understand the initial steps of the catalyzed hydrolysis reaction at catalyst-Si interface during the planarization. The removal mechanism is expected to be similar to that in SiC and SiO2.

Scopus

Publishing type：Research paper (international conference proceedings)  

To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin silicon carbide (SiC) wafers with a high removal rate by conventional mechanical processing because their hardness and brittleness cause cracks and chips during thinning. Therefore, the authors have attempted to thin SiC wafers using plasma chemical vaporization machining (PCVM), which is plasma etching using high-pressure plasma. PCVM has a high removal rate because of the high radical density in the high-pressure plasma, and it does not form a damaged layer on the processed surface because of the low ion energy. The authors have already achieved a very high removal rate of 15.6 μm/min by PCVM. However, many etch pits were generated on the wafer during PCVM in these high-speed machining conditions. Therefore, this study, using molten potassium hydroxide (KOH) etching, investigated the cause of such etch pits and found that they may stem from threading screw dislocation in the wafers. In addition, this research considered a process for reducing an etch pit size and succeeded in doing so by controlling wafer temperature.

DOI： 10.4028/www.scientific.net/MSF.1004.161

Scopus

Language：Japanese   Publisher：公益社団法人 精密工学会  

我々はSiC基板の新たな平坦化加工技術として光酸化を援用した触媒表面基準エッチング法の開発を行っている．さらに，現在では光酸化を促進するため，基板への逆バイアス印加を提案している．しかしながら，高電圧を印加した場合，基板と接する触媒の表面電位まで上昇してしまい触媒活性が低下するため，加工速度の向上に限りがあった．本研究では触媒の表面電位を制御することで更なる高能率化を目指した．

DOI： 10.11522/pscjspe.2019a.0_28

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A catalytically assisted etching system was developed for the ultra-precision fabrication of optical components, such as X-ray mirrors and extreme-ultraviolet mask blanks. This study demonstrates that an atomically smooth surface with a sub-Angstrom root-mean-square roughness could be achieved on a SiO2 glass substrate using pure water and Pt as the etching solution and catalyst, respectively. Density functional theory calculations confirmed that the mechanistic pathway was involved in catalyzed hydrolysis. The significant roles of the catalyst were clarified to be the dissociation of water molecules and the stabilization of a meta-stable state, in which a hypervalent silicate state is induced, and the Si-O backbond is elongated and loosened. To confirm the role of the catalyst, the Pt metal was replaced by Au, and the observed drastic difference in the removal rate was attributed to the degree of stabilization of the metastable state. Published under license by AIP Publishing.

DOI： 10.1063/1.5090320

Web of Science

PubMed

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.20965/ijat.2019.p0246

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5066105

PubMed

Publishing type：Research paper (international conference proceedings)  

Scopus

Publishing type：Research paper (international conference proceedings)  

© 2019 Trans Tech Publications Ltd, Switzerland. Catalyst-referred etching (CARE) is an abrasive-free and damage-free polishing method that involves applying a catalytic reaction at the contact point of the catalyst surface and workpiece in a chemical solution. An atomically flat silicon carbide (SiC) wafer surface can be obtained by the CARE process. Recently, it was found that water can be used as a chemical solution, even in the case of SiC polishing. However, its current removal rate of 4H-SiC (0001) 4°off-axis substrate is only 2 nm/h and is expected to increase. In this study, the use of photoelectrochemical oxidation in combination with the CARE process using water was investigated, successfully increasing the removal rate up to approximately 100 nm/h.

DOI： 10.4028/www.scientific.net/MSF.963.525

Scopus

Publishing type：Research paper (international conference proceedings)  

A novel abrasive-free method called catalyst-referred etching (CARE) is used for planarization of SiC In this method, a thin platinum (Pt) catalyst layer is deposited on an elastic pad. The planarization is performed by rotating the catalyst pad in contact with a wafer surface in water. After the planarization, SiC surfaces are atomically smooth with a root-mean-square (RMS) roughness of less than 0.1 nm over a whole wafer. Thanks to the use of pure water as the etchant, CARE is an environmentally friendly planarization method and potentially applicable to planarization of many functional materials, including GaN and oxides surfaces. However, the practical application of CARE is limited due to its low material removal rate (MRR) when using a Pt catalyst. Therefore, improving its MRR is highly demanded. Our recent research indicated that the etching proceeds via dissociative adsorption of water molecules onto Si-C bonds at topmost Si atoms. The lower activation barrier in the presence of the Pt catalyst is mainly due to the chemical stabilization resulting from the formation of Pt-0 bonds at the Pt-SiC interface. Accordingly, the reaction will be promoted by tuning the binding energy with O using other catalysts. Therefore, we experimentally investigate the dependence of MRR on various catalyst materials. The study reveals that Ni and Ru have high catalytic performance. Compared to Pt, Ni and Ru have the higher binding energy with O. The stronger chemical bonds promote water dissociation and stabilization of chemical bonds at the catalyst-SiC interface, leading to lowering its activation barrier and enhancement of the etching reaction.

Scopus

Publishing type：Research paper (international conference proceedings)  

The removal rate using a Ni catalyst was higher than that using a Pt catalyst. However, it decreased with the processing time because the Ni surface was easily oxidized. Therefore, we proposed the electrochemical method to keep the Ni surface active. By repeating Ni plating and dissolution cycle, we stabilized the removal rate for at least 8 h and created an atomically flat surface on a SiO2 surface.

Scopus

Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Cambridge University Press (CUP)  

DOI： 10.1017/S1431927618013764

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Cambridge University Press (CUP)  

DOI： 10.1017/S1431927618013715

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OSA - The Optical Society  

We have developed the new hybrid adaptive X-ray mirror based on mechanical and piezo-driven deformation to realize precise shape controllability on a long-length mirror. The mechanical bender approximately provides the required ellipse, while the piezoelectric actuators attached to the mirror correct very small residual errors to satisfy the diffraction-limited condition. The mechanical bender significantly reduces the role of the piezoelectric actuator, resulting in the suppression of accuracy degradation due to the drift and/or junction effect of the piezoelectric actuators. In addition, line focusing was demonstrated with two different numerical apertures at SPring-8, and the obtained beam sizes were 127 and 253 nm (FWHM), which agree well with the diffraction-limited sizes.

DOI： 10.1364/OE.26.017477

Scopus

PubMed

Language：English  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A comprehensive study of the physicochemical interactions and the reaction mechanism of SiC etching with water by Pt catalysts can reveal key details about the surface treatment and catalytic phenomena at interfaces. Therefore, density functional theory simulations were performed to study the kinetics of Pt-assisted water dissociation and breaking of a Si-C bond compared to the HF-assisted mechanism. These calculations carefully considered the elastic and chemical interaction energies at the Pt-SiC interface, activation barriers of Si-C bond dissociation, and the catalytic role of Pt. It was found that the Pt-catalyzed etching of SiC in water is initiated via hydrolysis reactions that break the topmost Si-C bonds. The activation barrier strongly depends on the elastic and chemical interactions. However, chemical interactions are a dominant factor and mainly contribute to the lowering of the activation barrier, resulting in an increased rate of reaction. (C) 2018 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.57.055703

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Physics Inc.  

In this study, the systematic errors of an X-ray single-grating interferometer based on the Talbot effect were investigated in detail. Non-negligible systematic errors induced by an X-ray camera were identified and a method to eliminate the systematic error was proposed. Systematic-error-free measurements of the wavefront error produced by multilayer focusing mirrors with large numerical apertures were demonstrated at the SPring-8 Angstrom Compact free electron LAser. Consequently, wavefront aberration obtained with two different cameras was found to be consistent with an accuracy better than λ/12.

DOI： 10.1063/1.5026440

Scopus

PubMed

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Union of Crystallography  

The performance of a hard X-ray split-and-delay optical (SDO) system with a wavefront division scheme was investigated at the hard X-ray free-electron laser facility SACLA. For the wavefront division, beam splitters made of edge-polished perfect Si(220) crystals were employed. We characterized the beam properties of the SDO system, and investigated its capabilities for beam manipulation and diagnostics. First, it was confirmed that shot-to-shot non-invasive diagnostics of pulse energies for both branches in the SDO system was feasible. Second, nearly ideal and identical focal profiles for both branches were obtained with a spot size of â1/41.5μm in full width at half-maximum. Third, a spatial overlap of the two focused beams with a sub-μm accuracy was achieved by fine tuning of the SDO system. Finally, a reliable tunability of the delay time between two pulses was confirmed. The time interval was measured with an X-ray streak camera by changing the path length of the variable-delay branch. Errors from the fitted line were evaluated to be as small as ±0.4ps over a time range of 60ps.The performance of a hard X-ray split-and-delay optical system with a wavefront division scheme has been investigated at SACLA.

DOI： 10.1107/S1600577517014023

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

We present new diagnostics for use in optical laser pump - X-ray Free Electron Laser (XFEL) probe experiments to monitor dimensions, intensity profile and focusability of the XFEL beam and to control initial quality and homogeneity of targets to be driven by optical laser pulse. By developing X-ray imaging, based on the use of an LiF crystal detector, we were able to measure the distribution of energy inside a hard X-ray beam with unprecedented high spatial resolution (∼1 μm) and across a field of view larger than some millimetres. This diagnostic can be used in situ, provides a very high dynamic range, has an extremely limited cost, and is relatively easy to be implemented in pump-probe experiments. The proposed methods were successfully applied in pump-probe experiments at the SPring-8 Angstrom Compact free electron LAser (SACLA) XFEL facility and its potential was demonstrated for current and future High Energy Density Science experiments.

DOI： 10.1016/j.mre.2018.01.006

Scopus

Language：Japanese  

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study, a gallium nitride (GaN) substrate produced was planarized using catalyst-referred etching (CARE). To improve the removal rate, the GaN substrate was processed using CARE-assisted photoelectrochemical (PEC) reaction (PEC CARE); the removal rate was 77 nm/h. However, the shape was embossed because of subsurface scratches introduced during preprocessing. These scratches were removed when the PEC CARE process was conducted under an applied potential of 2.5 V; The removal rate was 800 nm/h. In addition, a smooth surface of surface roughness 0.4 nm rms was obtained. A surface with step-terrace structures on the entire substrate was subsequently obtained when the CARE process was performed using a platinum (Pt) catalyst and deionized water; in this case, the surface roughness was 0.11 nm rms and the removal rate was 5 nm/h.

DOI： 10.1299/jsmemecj.2018.s1630004

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media, LLC  

We present here a new diagnostics based on using LiF crystal detectors that are able to perform measurements an intensity distribution of X-rays beams with diameters ranging from some microns up to some centimetres with high spatial resolution (~1 µm). In situ, 3D visualization of SACLA XFEL focused beam profile along propagation, including propagation inside photoluminescence solid materials, is demonstrated. Also, a high spatial resolution control a quality of targets used in optical laser pump—XFEL probe HEDS experiments is proposed.

DOI： 10.1007/978-3-319-73025-7_17

Scopus

Publishing type：Research paper (international conference proceedings)  

A novel abrasive-free method called catalyst-referred etching (CARE) has been developed in our group. In this method, a platinum film as a catalyst is deposited on an elastic pad that is rotated in contact with a wafer surface in water. After CARE planarization, SiC surfaces are atomically smooth with a root-mean-square (RMS) roughness of less than 0.1 nm over a whole wafer. Using only pure water as an etchant, CARE is a promising planarization method and potentially applicable to planarization of many semiconductor surfaces, including GaN and oxides surfaces. However, the removal rate (RR) of SiC via CARE using a Pt catalyst is quite low, limiting its practical application. Our recent research on the removal mechanism using density functional theory (DFT) calculations indicated that the etching proceeded via a dissociative adsorption of water molecules onto the Si-C bonds at the topmost Si surface, catalyzed by a Pt catalyst. We expect that the RR can be improved by using the higher reactivity catalyst. Therefore, we experimentally investigate the dependence of RR on various catalyst materials. The results indicate that SiC can be planarized with a high RR using 3d transition metal catalysts. Using DFT calculations, we clarify that a high catalytic reactivity of a 3d transition metal is attributed to the higher chemical binding energy with OH, compared to that of Pt. This high chemical bond promotes water dissociation and stabilizes metastable states by forming chemical bonds at the catalyst-SiC interface, leading to lowering its activation barrier and an enhancement of the etching reaction.

Scopus

Publishing type：Research paper (international conference proceedings)  

We have developed "Catalyst Referred Etching" (CARE) using pure water as an etchant and Pt as a catalyst as a new polishing method. Using CARE, many functional materials, such as silicon carbide (SiC), gallium nitride (GaN), and metal oxides, can be planar-ized to atomically well-ordered surfaces with a root-mean-square (RMS) roughness of less than 0.1 nm over a whole wafer. The planarized surface has a step-and-terrace structure, indicating that CARE is step-flow etching type. Thus, the material removal rate (MRR) of CARE using a Pt catalyst, especially for crystalline materials, is quite low, approximately 20 nm/h for SiC. Our recent study shows that the catalytic reactivity of a Ni for CARE is higher than that of a Pt. Additionally, compared to Pt, Ni is cost-effective and abundant, indicating that Ni is a promising catalyst for CARE. However, the MRR using a Ni catalyst usually decreases with the processing time due to catalytic deactivation by oxidation of the Ni surface. Therefore, we use electrochemical deposition method to control Ni surface condition and to keep its surface catalytivally active. First, before CARE processing, the Ni is deposited on a polishing pad by setting its potential to be lower than that of the etchant. The deposited Ni layer works as an active catalyst. Second, after CARE processing, the residual Ni is dissolved into the etchant by changing its potential to be higher than that of the etchant. By alternative repeating these steps, reactive Ni on the polishing pad is continually prepared. Accordingly, the removal rate is stable with processing time. The study reveals that CARE with the potential control method is potential for high-efficiency polishing of functional materials.

Scopus

Language：English  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Cutting-edge hard X-ray microscopy strongly depends on sophisticated focusing optics and ultrabright X-ray sources at synchrotron-radiation and X-ray free-electron laser (XFEL) facilities. These facilities typically provide two-dimensional nanofocusing X-ray beams by combining one-dimensional focusing mirrors. However, single-reflecting two-dimensional focusing mirrors with an ellipsoidal surface, which are well-known to possess high efficiency, have limited microfocusing applications. In this paper, we present an ultrahigh-precision ellipsoidal mirror for two-dimensional X-ray nanofocusing by overcoming the difficulties faced in the manufacturing process of its aspherical surface, including the surface-processing methods and surface metrology. The developed mirror has nanoscale accuracy, and it achieves focus size of 85 nm x 125 nm (full width at half maximum) using 7-keV X-rays. Two-dimensional focus was demonstrated in the same focal plane by resolving 50-nm test structures by scanning X-ray microscopy using a focusing beam. These achievements represent an important first step toward realizing two-dimensional aspherical mirrors with complex designs, in addition to ultralow loss and unprecedented small focusing property for extensive optical applications in synchrotron-radiation and XFEL facilities as well as in other scientific fields that require ultraprecision optical surfaces.

DOI： 10.1038/s41598-017-16468-1

Web of Science

PubMed

Language：Japanese  

Language：Japanese  

Language：English  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

High resolution imagery of the Sun's X-ray corona provides an essential clue in understanding dynamics and heating processes of plasma particles there. However, X-ray imagery of the Sun with sub-arcsecond resolution has so far never been conducted due to severe technical difficulty in fabricating precision Wolter mirrors. For future X-ray observations of the solar corona, we are attempting to realize precision Wolter mirrors with sub-arcsecond resolution by adopting advanced surface polish and metrology methods to sector mirrors which consist of a portion of an entire annulus, by direct polishing onto the mirror substrate.
Based on the knowledge obtained through fabrication of the first (in 2013) and second (in 2014) engineering Wolter mirrors and subsequent evaluations on their X-ray focusing performance, the third engineering mirror was made in 2015-2016. The primary target of improvement over the second mirror was to suppress figure error amplitude especially for spatial frequencies around 1 mm(-1) and to suppress the large astigmatism that was present in the second mirror, by introducing improved deterministic polish and smoothing on the precision mirror surfaces (32.5 mm x 10 mm in area for both parabola and hyperbola segments), as well as by careful characterization of the systematic error in the figure measurement system for the precision polish. Measurements on the focusing performance of thus-fabricated third Wolter mirror at SPring-8 synchrotron facility with 8 keV X-rays demonstrated that the mirror attained sub-arcsecond focusing performance with its HPD (half-power diameter) size reaching as small as similar to 0.2 arcsec for meridional focusing while similar to 0.1 arcsec for sagittal focusing. The meridional focusing achieved nearly diffraction limited performance (similar to 0.12 arcsec FWHM for the PSF core). We also confirmed that the large astigmatism noted in the second mirror was correctly removed in the third mirror with the correction of the above-mentioned systematic error.

DOI： 10.1117/12.2273507

Web of Science

Language：English  

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Language：Japanese   Publisher：公益社団法人 精密工学会  

高精度なX線全反射ミラーを4枚用いて，高分解能かつ色収差のない結像型X線顕微鏡を開発した．本顕微鏡の実用性を確かめるために，蛍光X線イメージング，暗視野イメージング，位相イメージングを実施した．暗視野イメージングでは，後焦点位置にナイフエッジを挿入した．位相イメージングでは，位相回折格子を用いたタルボ効果を利用した．ポリスチレン球や金属微粒子，テストチャートの観察について詳細に報告する．

DOI： 10.11522/pscjspe.2017S.0_957

Language：Japanese  

Language：English  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

We developed a single-shot X-ray spectrometer for wide-range high-resolution measurements of Self-Amplified Spontaneous Emission (SASE) X-ray Free Electron Laser (XFEL) pulses. The spectrometer consists of a multi-layer elliptical mirror for producing a large divergence of 22 mrad around 9070 eV and a silicon (553) analyzer crystal. We achieved a wide energy range of 55 eV with a fine spectral resolution of 80 meV, which enabled the observation of a whole SASE-XFEL spectrum with fully-resolved spike structures. We found that a SASE-XFEL pulse has around 60 longitudinal modes with a pulse duration of 7.7 +/- 1.1 fs.

DOI： 10.3390/app7060584

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Chemical etching of SiC was found to proceed in pure water with the assistance of a Pt catalyst. A 4H-SiC (0001) wafer was placed and slid on a polishing pad in pure water, on which a thin Pt film was deposited to give a catalytic nature. Etching of the wafer surface was observed to remove protrusions preferentially by interacting with the Pt film more frequently, thus flattening the surface. In the case of an on-axis wafer, a crystallographically ordered surface was obtained with a straight step-and-terrace structure, the height of which corresponds to that of an atomic bilayer of Si and C. The etching rate depended upon the electrochemical potential of Pt. The vicinal surface was observed at the potential at which the Pt surface was bare. The primary etching mechanism was hydrolysis with the assistance of a Pt catalyst. This method can, therefore, be used as an environmentally friendly and sustainable technology. Published by AIP Publishing.

DOI： 10.1063/1.4983206

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-workingdistance properties. An advanced Kirkpatrick-Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a similar to 1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10 keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20 h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles.

DOI： 10.1038/srep46358

Web of Science

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

We propose the use of two pairs of concave-convex mirrors as imaging optics for the compact full-field x-ray microscope with high resolution and magnification factors. The optics consists of two pairs of hyperbolic convex and elliptical concave mirrors with the principal surface near the object, consequently enabling the focal length to be 10 times shorter than conventional advanced Kirkpatrick-Baez mirror optics. This paper describes characteristics of the optics calculated by ray-tracing and wave-optical simulators. The expected spatial resolution is approximately 40 nm with a wide field of view of more than 10 mu m and a total length of about 2 m, which may lead to the possibility of laboratory-sized, achromatic, and high-resolution full-field x-ray microscopes. (C) 2017 Optical Society of America

DOI： 10.1364/AO.56.000967

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We have observed the lattice expansion before the onset of compression in an optical-laser-driven target, using diffraction of femtosecond X-ray beams generated by the SPring-8 Angstrom Compact Free-electron Laser. The change in diffraction angle provides a direct measure of the lattice spacing, allowing the density to be calculated with a precision of +/- 1%. From the known equation of state relations, this allows an estimation of the temperature responsible for the expansion as &lt;1000 K. The subsequent ablation-driven compression was observed with a clear rise in density at later times. This demonstrates the feasibility of studying the dynamics of preheating and shock formation with unprecedented detail. Published by AIP Publishing.

DOI： 10.1063/1.4976541

Web of Science

Language：English   Publishing type：Part of collection (book)   Publisher：Springer Japan  

Recent technological developments have enabled the imaging of chemical elements in cells, although quantitative analyses, such as by inductively coupled plasma mass spectrometry, were developed previously. Applications allowing high-resolution imaging at the single-cell level are anticipated in cell biology and medicine, where the roles of elements, especially in relation to intracellular molecules such as proteins, nucleic acids, lipids, and sugars, are essential for understanding cellular functions. The expression of proteins and genes varies depending on cellular function, and multiple elements are likely to be associated with biological molecules in the functioning of cell proliferation, differentiation, aging, and stress responses. In this review, we describe a scanning X-ray fluorescence microscopy system, which can reliably determine the cellular distribution of multiple elements by a sub-100-nm focusing approach, together with its applications. Visualizing intracellular elements and understanding their dynamics at the single-cell level may provide great insight into their behaviors.

DOI： 10.1007/978-4-431-56463-8_3

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT UNION CRYSTALLOGRAPHY  

X-ray science has greatly benefited from the progress in X-ray optics. Advances in the design and the manufacturing techniques of X-ray optics are key to the success of various microscopic and spectroscopic techniques practiced today. Here the generation of apodized X-ray illumination using a two-stage deformable Kirkpatrick-Baez mirror system is presented. Such apodized illumination is marked by the suppression of the side-lobe intensities of the focused beam. Thus generated apodized illumination was employed to improve the image quality in scanning X-ray fluorescence microscopy. Imaging of a non-isolated object by coherent X-ray diffractive imaging with apodized illumination in a non-scanning mode is also presented.

DOI： 10.1107/S1600577516017677

Web of Science

Scopus

PubMed

Language：Japanese  

Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.83.300

CiNii Books

Language：Japanese   Publisher：公益社団法人 精密工学会  

我々は，窒化ガリウム (GaN) 基板を平坦化する革新的な手法として触媒表面基準エッチング (Catalyst-Referred Etching; CARE) 法の開発，研究を行っている．現在までに研磨定盤にPt触媒，加工液に純水を用いて，原子レベルに平坦な表面が作製可能となっているが，ステップフロー型であるのでCARE法は加工速度が不十分である．そこで本研究では，GaN基板の高能率平坦化を目指し，光電気化学酸化を援用したCARE法（PEC-CARE加工）を検討することで，加工速度は800 nm/hにまで向上した．

DOI： 10.11522/pscjspe.2017a.0_19

Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.11522/pscjspe.2017S.0_541

Language：Japanese   Publisher：公益社団法人 精密工学会  

SiCデバイス製造工程においてサブ大気圧プラズマを用いたプラズマエッチング加工を検討している。今回、実用化を視野に入れた加工速度を達成することを目指した。SF6の供給量と投入電力を増大させ、反応種であるFラジカル数を増加させることで加工速度を向上させた。大電力の投入はこれまで困難であったが、新たな試料台を用いることで大電力を投入しても安定なプラズマの発生に成功し、2インチウエハ全面加工速度15.2 μm/minを達成した。

DOI： 10.11522/pscjspe.2017S.0_975

Language：Japanese   Publisher：公益社団法人 精密工学会  

我々はこれまで触媒表面基準エッチング法の開発を行ってきた。本手法ではエッチング反応による加工が、触媒作用を有する研磨パッドの近傍のみで進行するため凸部からの選択的な加工が可能である。砥粒等の機械的作用によるダメージはなく効率的に基準面形状の転写が可能である。本研究では、水素水を用い触媒表面の加工生成物を除去することで加工速度の安定化を行い、加工液のpHを変化させることで加工速度の向上に成功した。

DOI： 10.11522/pscjspe.2017A.0_1

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

Modern surface processing of semiconductors or oxide materials requires highly precise temporal control of each processing step. In addition, large wafers must be processed quickly for high throughput. We have developed a numerically controlled sacrificial oxidation method with atmospheric-pressure plasma using electrode arrays. In this method, we oxidized the surface of a wafer with atmospheric-pressure plasma applied precisely by an electrode array, and then dipped the wafer in HF solution to remove the surface oxide layer. The plasma process time can be controlled independently at each electrode area. The oxidation rate and surface profile of the treated wafer are crucial for precision processing. We investigated the oxidation rate of atmospheric-pressure plasma oxidation by spectroscopic ellipsometry and examined the surface morphologies of untreated and treated wafers by atomic force microscopy. The surface profile smoothness correlated with the plasma oxidation time and electrode voltage during oxidation. The surface roughness tended to increase when the sample was oxidized for longer times with higher electrode voltage. This correlation between surface roughness and oxidation time resembled the results of Si/SiO2 interfacial roughness in the case of thermal oxidation. In the plasma sacrificial oxidation process, the increase of surface roughness at the Si/SiO2 interface by plasma oxidation must be considered.

DOI： 10.4028/www.scientific.net/KEM.723.242

Scopus

Language：Japanese   Publisher：公益社団法人 精密工学会  

X線自由電子レーザーは超高強度という非常に優れた性質をもつ．その性能をより向上させるためには，高精度かつ大開口数であるX線集光光学系の開発が必要不可欠である．我々は，大開口数多層膜ミラーを用いた集光光学系をSPring-8に構築した．そして，X線グレーチング干渉計で波面計測を行うことによって多層膜ミラーの作製誤差を計測しさらにこれを修正した．&lambda;/4程度の精度で多層膜集光ミラーを完成させた．

DOI： 10.11522/pscjspe.2017S.0_959

Language：Japanese   Publisher：公益社団法人 精密工学会  

我々は機能性材料を平坦化する手法として触媒表面基準エッチング法を開発してきた．加工液に純水，触媒にPt，を用いる本手法は高精度表面の実現を可能にするがステップフロー型エッチングであるため加工速度は未だ不十分である．そこで本研究ではニッケルを触媒として利用し，加工速度の向上を図った．表面が酸化され化学的不活性になりやすいニッケルを電気化学的手法によりその触媒活性を安定させ超高速加工を実現した．

DOI： 10.11522/pscjspe.2017A.0_35

Publishing type：Research paper (international conference proceedings)  

A novel abrasive-free planarization method called catalyst-referred etching (CARE) has been invented and developed in our group. In this method, a platinum film, which acts as a catalyst, is deposited on an elastic pad that is rotated in contact with a wafer surface in water. CARE can produce flat, undamaged, and smooth SiC and SiO2 surfaces with a root-mean-square (RMS) roughness of less than 0.1 nm over a whole wafer. The mechanism is considered a dissociative adsorption of water molecules onto the Si-C bonds at the topmost Si surface. The gross activation barrier strongly correlates with the stability of the metastable state and is reduced by the formation of Pt-O chemical bonds, leading to an enhancement of the etching reaction.

Scopus

Publishing type：Research paper (international conference proceedings)  

A novel planarization method termed catalyst-referred etching (CARE) was developed, in which platinum and pure water were respectively employed as a catalyst and an etchant to create highly ordered surfaces with a step terrace structure on oxide materials, such as quarts, sapphire, and zinc oxide substrates. The step heights were in good agreement with the theoretical single-bilayer thickness. However, the removal rate of the etching process gradually decreased with the processing time. This decrease in the removal rate was attributed to degradation of the catalyst via the adsorption of silicic acid produced during the CARE process on the catalyst surface. Two methods were employed to remove the silicic acid: control of the potential of the Pt surface and cleaning of the catalyst pad with H2 water. The removal rate was maintained by using both methods. In both methods, the potential of the Pt surface was set at the H generation level. It is proposed that the generated hydrogen atoms broke the Pt-O bonds, thereby maintaining the reactivity of the catalyst surface.

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