研究者詳細 - 石丸　学

論文 - 石丸　学

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Radiation-induced short-range order in ceramics 招待有り査読有り国際誌

Ishimaru M.

Microscopy 75 ( 3 ) 217 - 228 2026年06月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：記事・総説・解説・論説等（学術雑誌）

The development of radiation-tolerant materials is of technological importance for establishing safe operating systems in the nuclear industry, from power generation to the immobilization of high-level radioactive waste. Harsh radiation environments generate interstitials and vacancies in materials, and their accumulation leads to structural changes, including order-to-disorder phase transformations and amorphization. These structural changes are induced locally on an atomic scale; therefore, transmission electron microscopy is a useful technique for analyzing radiation effects in materials. In addition, the strong interaction between matter and electrons enables the detection of weak signals associated with phase transformations, such as diffuse scattering and halo rings. This article provides an overview of radiation-induced amorphous structures in materials consisting of light elements, such as boron carbide and silicon oxycarbide, as well as the short-range ordered structure that appears during an order-to-disorder phase transformation in fluorite structural derivatives.

DOI： 10.1093/jmicro/dfaf053

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Diffusion and trapping of silicon in wurtzite gallium nitride 査読有り国際誌

Mimura K., Nakamura R., Ishimaru M., Sakane S., Ueoka Y., Mesuda M., Suzuki T.

Materials Science in Semiconductor Processing 204 2026年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

The diffusion behavior of various dopants in gallium nitride (GaN) should be comprehensively understood as essential for materials design and for controlling of the electrical properties towards versatile device applications. This study measures the diffusion coefficient (D) of a typical n-type dopant, silicon (Si), along the c-axis direction in monocrystalline GaN (mc-GaN) films with the wurtzite structure at the relatively low temperature range of 600–900 °C compared to previous reports. Two types of samples are examined using secondary ion mass spectrometry. In the case of a thin Si layer deposited on mc-GaN, the D values are determined by analyzing the Si concentration profiles based on an error-function type equation, yielding values in the range of 5.1 × 10<sup>−21</sup> – 3.0 × 10<sup>−19</sup> m<sup>2</sup> s<sup>−1</sup>. The activation energy for Si diffusion is 1.07 eV, which is comparable with the data reported in the literature for the measurements above 900 °C. In contrast, no Fickian diffusion of Si is observed in a diffusion couple of an epitaxially-grown GaN film containing Si, GaN(Si), on mc-GaN at 600–900 °C. Cross-sectional transmission electron microscopy reveals that the microstructure of the GaN(Si) layer is highly defective; not only do boundaries between columns exist, but numerous dislocations are also present throughout the layer, serving as trapping sites for Si.

DOI： 10.1016/j.mssp.2025.110272

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イオン照射δ-Sc<sub>4</sub>Hf<sub>3</sub>O<sub>12</sub>に出現する特異な短範囲規則構造査読有り

岩崎将成, 石丸学

まてりあ ( 公益社団法人日本金属学会 ) 65 ( 1 ) 23 - 23 2026年01月

低エネルギーの電子ビームが励起するアモルファスゲルマニウム薄膜の瞬間•広域結晶化査読有り

仲村龍介, 奥川将行, 石丸学

まてりあ ( 公益社団法人日本金属学会 ) 65 ( 1 ) 19 - 19 2026年01月

Diffusion of Oxygen in Amorphous and Monoclinic (Hf,Zr)O2 Films 査読有り国際誌

Motozu Y., Nakamura R., Ishimaru M., Suzuki T.

Physica Status Solidi B Basic Research 263 ( 1 ) 2026年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

The diffusion coefficients of oxygen (D) in thin films of amorphous (a-) and nanocrystalline monoclinic (Hf,Zr)O<inf>2</inf> are determined by profiling the long-range diffusion of the stable oxygen isotope (<sup>18</sup>O) in the temperature range of 300°C–700°C using secondary-ion mass spectrometry. D at 300°C–400°C in the a-phase and D at 500°C–700°C in the m-phase exhibit a nearly continuous temperature dependence. The activation energy for diffusion in the a-phase is found to be 1.42–2.91 eV, depending on the degree of structural relaxation, and is comparable to or higher than that for volume diffusion in the m-phase (0.48–1.59 eV, including literature data). The pair distribution functions for the a-phase, obtained using electrons as a probe, indicate that the local structure resembles that of an m-phase model from a previous molecular dynamics simulation. Supported by previously reported theoretical calculations, the possible diffusion mechanisms of oxygen in both the a-phase and m-phase are discussed.

DOI： 10.1002/pssb.202500490

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Giant spin-orbit torque induced by spin Hall effect in amorphous Pt(P) alloys 査読有り国際誌

Shashank U., Tomoda T., Mathew A.J., Vashisht G., Imai K., Kusaba Y., Dong C.L., Chen C.L., Horibe Y., Ishimaru M., Awano H., Asada H., Fukuma Y.

Npg Asia Materials 17 ( 1 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report a giant spin-orbit torque (SOT) induced by spin Hall effect (SHE) in amorphous Pt(P) alloys, which is confirmed by magnetization switching and spin torque-ferromagnetic resonance measurements. Pt(P) is fabricated by ion-implantation technique using energies from 10 to 30 keV with doses ranging from 2.5 × 10<sup>16</sup> to 10 × 10<sup>16</sup> ions/cm<sup>2</sup>. The P-ion implantation process causes distortion and defects in the fcc structure of the as-deposited Pt layer and changes it to an amorphous structure as the accelerating energy as well as the dose increases, leading to a decrease in the electrical conductivity. However, we can obtain a higher spin Hall conductivity, σxySH of 3.62×103ℏ2eΩ−1cm−1 for Pt(P) as compared to that of 1.03×103ℏ2eΩ−1cm−1 for pure Pt. The spin Hall efficiency, θSH is drastically increased up to 1.17 for Pt(P) with 30 keV energy and dose of 7.5 × 10<sup>16</sup> ions/cm<sup>2</sup>. We also observe a significant reduction in the critical switching current density, Jsw of the SOT magnetization switching from 1.5 × 10<sup>11</sup> A/m<sup>2</sup> for pure Pt to 3.0 × 10<sup>10</sup> A/m<sup>2</sup> for Pt(P). Such a giant SHE can reduce the power consumption to control the magnetization by using SOT, and therefore our findings may provide an alternate path to enhance θSH by using amorphous materials with a variety of elements, beyond crystalline solids.

DOI： 10.1038/s41427-025-00596-6

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The effective thermal conductivity of a screen-printed thermoelectric film of Bi2Te3 and CsSnI3 査読有り国際誌

Miyazaki K., Mustafa A., Baranwal A.K., Saini S., Watanabe K., Miura A., Yabuki T., Ishimaru M., Kawano S., Wang Q., Iikubo S., Shen Q., Hayase S.

International Journal of Heat and Mass Transfer 250 2025年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In recent years, printed thermoelectric thin films have attracted attention due to their advantages in enabling large-area and flexible designs. We developed printable thermoelectric composites of bismuth telluride and halide perovskite, which were expected to exhibit superior thermoelectric properties compared to other printable materials, such as conductive organic materials. The measured dimensionless figure of merit was about 0.1 at room temperature due to its low thermal conductivity. We assessed the interfacial thermal resistance between bismuth telluride and halide perovskite using multilayered films to understand the measured low thermal conductivity. The calculated thermal conductivity using the measured interfacial thermal resistance was fairly consistent with the effective thermal conductivity observed. We also discussed the interfacial thermal resistance using a phonon transport model based on ab-initio calculations to confirm the validity of our measurements. Additionally, we found that the high interfacial thermal resistance was achieved due to the low group velocities of both materials in the composites. This mechanism can be applied not only to improve thermoelectric materials but also to address thermal issues in composites.

DOI： 10.1016/j.ijheatmasstransfer.2025.127292

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Heterogeneous amorphous structure and bioactivity in silver-doped bioactive glasses synthesized by spray drying methods 査読有り国際誌

Araki F., Lin M.Z., Shih S.J., Ishimaru M.

Advanced Powder Technology 36 ( 11 ) 2025年11月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, Ag-doped SiO<inf>2</inf>-CaO-P<inf>2</inf>O<inf>5</inf> bioactive glasses (BGs) were synthesized by a spray drying method, and their atomistic structures were investigated by transmission electron microscopy, X-ray diffraction, and nuclear magnetic resonance. The constituent elements (Si, Ca, P, and O) were homogeneously distributed in the pure (non-doped) BG, but a small Ca- and P-rich layer was present on the surface. The segregation of Ca and P on the surface became more pronounced with increasing Ag concentration. The atomic pair-distribution functions extracted by nanobeam electron diffraction revealed that the Ag-doped BG particles had a heterogeneous amorphous structure: the interior and surface of the BG particles were similar to those of SiO<inf>2</inf> and phosphate-based glasses, respectively. The addition of Ag resulted in less non-bridging oxygen, which may be due to the removal of the network modifier ion (Ca) from the SiO<inf>2</inf> network. In vitro bioactive tests of the pure BG and Ag-doped BG particles revealed that the formation of hydroxyapatite was enhanced by Ag doping, although the amount of non-bridging oxygen decreased. This is attributed to the P- and Ca-rich surface layer, which triggers the nucleation and growth of hydroxyapatite.

DOI： 10.1016/j.apt.2025.105054

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Radiation-induced modifications in ZrN: effect of micro vs. nano crystallites 査読有り国際誌

Beer C., Bahri M., Baldinozzi G., Ishimaru M., Zhang Y., Sharpe M.K., McAleese C.D., Chen X., Bohns F., Manning T., Browning N.D., Whittle K., Springell R., Akhtar R., Patel M.

Acta Materialia 298 2025年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

ZrN is a model system used to understand the irradiation response of isostructural advanced nuclear fuel, UN. UN possesses desirable material properties, such as improved thermal conductivity and fissile uranium density compared to oxides, but understanding damage accumulation and recovery processes in its rocksalt structure remains limited. Micro- and nanocrystalline ZrN were studied under ion irradiation using 600 keV Ar<sup>+</sup> ions with fluences varying from 1 × 10<sup>15</sup> to 1 × 10<sup>17</sup> ions/cm<sup>2</sup> at room temperature. Structural parameters, crystallite size, and microstrain of crystalline phases were determined via a unique Rietveld refinement of glancing incidence XRD data. Transmission electron microscopy was used to investigate microstructural modifications, and nanoindentation was used to explore the evolution of mechanical properties. The results show a pronounced increase in the crystallite size of nanocrystalline ZrN, while induced damage degrades the coherence of scattering domains in both ZrN systems post-irradiation. Microcrystalline ZrN displays swelling with increasing fluence, whereas nanocrystalline ZrN contracts before showing a continued unit cell expansion at higher fluences. AFM was used to confirm swelling in mi-crocrystalline ZrN, while oxidation in nanocrystalline ZrN is explored using ToF-ERDA and is attributed to a radiation-induced REDOX reaction. Nanoindentation results confirmed increases in the post-irradiated surface hardness and elastic modulus. The TEM investigation provides evidence of periodic and incommensurate ordering in irradiated regions of microcrystalline ZrN. The formation of a distinct epitaxial layer of cubic ZrO<inf>2</inf> on the surface of microcrystalline ZrN has been attributed to the effects of incident ion interactions.

DOI： 10.1016/j.actamat.2025.121391

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Mode crossover of vortex pinning and excitation in segmented nanorod system 査読有り

Horide T., Torigoe K., Otsubo K., Ishimaru M.

Superconductor Science and Technology 38 ( 8 ) 2025年08月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

The nanorods are effective in improving the critical current density in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> films, but their pinning strength and morphology depend on the fabrication process. To understand the critical current density mechanism, the vortex excitation mode as well as static pinning configuration should be discussed. In this study, we prepared YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> + BaHfO<inf>3</inf>/YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> composite multilayers (CMLs). This is a segmented nanorod system where the length of nanorods can be controlled. Two types of CMLs were fabricated to extract the influence of the pinning strength of the nanorods, where the nanorod pinning strength is relatively represented by J<inf>c</inf>(77 K,1T) of a YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> + BaHfO<inf>3</inf> single layer film: 0.73 MA cm<sup>−2</sup> for strong-pinning nanorod and 0.08-0.27 MA cm<sup>−2</sup> for weak-pinning nanorod. In the multilayer with strong-pinning nanorods, the critical current density decreased with increasing the pure layer ratio, indicating that the vortex excitation from the nanorods was accelerated by the pure layer. In the multilayer with weak-pinning nanorods, dependence of the critical current density on the pure layer ratio exhibited the peak due to the competition of excitation modes. Surprisingly, when we compare the results in different types of CMLs, the critical current density for high pure layer ratio is almost the same despite different nanorod pinning strength, where the nanorod edges rather than the nanorod core is a dominant pinning center. Design of the excitation mode as well as static configuration is very effective in achieving high critical current density in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> films.

DOI： 10.1088/1361-6668/adfa4a

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Control of threading dislocation formation in epitaxially grown YBa2Cu3O7 thin films and their pinning properties 査読有り国際誌

Voulhoux M., Igarashi T., Horide T., Ishimaru M.

Journal of Applied Physics 137 ( 17 ) 2025年05月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

To improve the critical current density of c-axis oriented YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> (YBCO) thin films, much effort has been devoted to the introduction of pinning centers that disrupt vortex migration under magnetic fields. Threading dislocations are anticipated to act as one-dimensional pinning centers without reducing the superconducting regions. In this study, YBCO thin films were prepared on a SrTiO<inf>3</inf> (STO) + xCeO<inf>2</inf> (x = 0%, 30%, and 50%) buffer layer by pulsed-laser deposition, and their nanostructures were analyzed by transmission electron microscopy. The interface between the buffer layer and the YBCO thin film was flat for the pure STO, while it was roughened by numerous nanoparticles for the CeO<inf>2</inf>-doped buffer layer. Due to these nanoparticles, threading dislocations were introduced more densely in the YBCO films on the STO + CeO<inf>2</inf> buffer layer than in those on the pure STO buffer layer, depending on the volume percent of CeO<inf>2</inf>. Investigations of the critical current density as a function of the magnetic field revealed that the threading dislocations effectively act as pinning centers.

DOI： 10.1063/5.0249007

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Asymmetric self-organization from a symmetric film by phase separation 査読有り国際誌

Horide T., Usuki M., Ishimaru M., Horibe Y.

Nanoscale 17 ( 8 ) 4740 - 4749 2025年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Self-organization realizes various nanostructures to control material properties such as superconducting vortex pinning and thermal conductivity. However, the self-organization of nucleation and growth is constrained by the growth geometric symmetry. To realize highly controlled three-dimensional nanostructures by self-organization, nanostructure formation that breaks the growth geometric symmetry thermodynamically and kinetically, such as tilted or in-plane aligned nanostructures, is a challenging issue. A vertically aligned nano-checkerboard is typically formed from ZnMnGaO<inf>4</inf> with the twin domain vertically aligned by the stress from the MgO substrate. The change in the template structure is promising to form a different type of nanostructure. The cubic ZnMnGaO<inf>4</inf>/MgO films were annealed to form nanoscale tetragonal domains in the tilted direction from the surface, which is determined by lattice mismatch, lattice symmetry, and atomic bonding. On the other hand, as a result of free deformation, in-plane aligned twin domains were formed on the SrTiO<inf>3</inf> substrate with a thin MgO buffer layer, which does not induce stress in the ZnMnGaO<inf>4</inf> film. By annealing the ZnMnGaO<inf>4</inf>/MgO/SrTiO<inf>3</inf> film, the nano-checkerboard with a size of ∼10 nm and a length of ∼200 nm is elongated to the in-plane [100] or [001] direction. This study demonstrates the possibility of fabricating a nanostructure that breaks the growth geometric symmetry, which is not achieved by the previous self-organization. The phase separation with controlled template opens more complicated three-dimensional structures by self-organization.

DOI： 10.1039/d4nr04343j

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Short-range order in ion irradiated fluorite structural derivatives in Sc2O3–HfO2 査読有り国際誌

Izumi T., Iwasaki M., Patel M.K., Baldinozzi G., Grygiel C., Ishimaru M.

Acta Materialia 284 2025年01月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Knowledge of radiation-induced structural changes in complex oxides is of technological importance for the development of container materials for the immobilization of nuclear waste. Fluorite structural derivatives are candidates for container materials, but their disordering processes under radiation environments are still unclear. In the present study, ion irradiation was performed on the Sc<inf>2</inf>O<inf>3</inf>–HfO<inf>2</inf> pseudo-binary system in which fluorite-related structural compounds such as β–Sc<inf>2</inf>Hf<inf>7</inf>O<inf>17</inf>, γ–Sc<inf>2</inf>Hf<inf>5</inf>O<inf>13</inf>, and δ–Sc<inf>4</inf>Zr<inf>3</inf>O<inf>12</inf> exist, and the short-range ordered structures were investigated by transmission electron microscopy (TEM). The pristine long-range ordered rhombohedral phase was found to transform into a long-range disordered cubic oxygen-deficient fluorite phase upon ion irradiation. The atomic arrangements are not completely disordered, but a more ordered structure was present in the disordered fluorite matrix. A characteristic diffuse scattering was observed in the electron diffraction patterns, and dark-field TEM observations revealed that it is due to microdomains, defined as small regions where the degree of order is higher than that of the disordered matrix. Although the parent phase was different before irradiation, the short-range organization is the same. A comparison of diffuse scattering with the location of superlattice reflections suggested that the microdomains have a structure similar to the δ-phase. With increasing Sc<inf>2</inf>O<inf>3</inf> concentration, the microdomains of δ-type structures were suggested to change to short-range ordered bixbyite structures, which are not present in the equilibrium phase diagram.

DOI： 10.1016/j.actamat.2024.120581

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Fabrication of YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> Superconducting Nanocomposite Film on Silicon Substrate 査読有り

Bertrand A., Voulhoux M., Kuroki M., Ishimaru M., Horide T.

ACS Applied Electronic Materials 6 ( 6 ) 4601 - 4607 2024年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

Fabrication of YBa2Cu3O7 nanocomposite films on silicon substrates is required for superconducting electromagnetic devices. Low-temperature deposition is effective in suppressing the chemical reaction between YBa2Cu3O7 and Si, while sufficient diffusion is required to form the well-defined nanocomposite structure. The fabrication of the YBa2Cu3O7 nanocomposite films on Si substrates should simultaneously satisfy these conflicting requirements. A YSZ (yttrium stabilized zirconia) buffer layer was epitaxially grown on Si substrates to suppress the chemical reaction. Then, the YBa2Cu3O7 + Ba2YbNbO6 films were fabricated on the YSZ/Si. The nanorods with diameters of 9-17 nm were elongated along the c-axis even at the low deposition temperature. The YBa2Cu3O7 + Ba2YbNbO6 nanocomposite film exhibited a critical temperature of 86.0 K, which is comparable to the critical temperature of 85.6 K in the pure film. The irreversibility temperature was slightly improved by the nanorods. Thus, we demonstrate the formation of nanorods in the YBa2Cu3O7 films on Si substrates without lowering the critical temperature. This opens the superconducting electromagnetic devices integrated with high-temperature superconductors and semiconductors.

DOI： 10.1021/acsaelm.4c00612

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Stability of ion-beam-induced bixbyite phase in δ-Sc<inf>4</inf>Hf<inf>3</inf>O<inf>12</inf> under heat treatments and electron beam irradiations 査読有り

Iwasaki M., Patel M.K., Baldinozzi G., Sickafus K.E., Ishimaru M.

Journal of the European Ceramic Society 44 ( 5 ) 3131 - 3138 2024年05月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Oxygen-deficient compounds A4B3O12 have a δ-type structure with a regular long-range arrangement of oxygen vacancies induced by compensation of the charge difference between A3+ and B4+ cations, while A and B cations do not order long-range and only display weak short-range correlations. The δ-type compounds in the Sc2O3-HfO2 and Sc2O3-ZrO2 systems exhibit excellent resistance to radiation-induced amorphization, but the long-range ordered δ-phase was transformed into a short-range ordered bixbyite phase. Since this structural change was not predicted from the phase diagram, the validity of the formation of the bixbyite phase and its stability are still unclear. In the present study, the changes of radiation-induced microstructures in δ-Sc4Hf3O12 under heat treatments and electron beam irradiations were examined by ex-situ and in-situ transmission electron microscopy. It was found that the ion-beam-induced metastable bixbyite phase is transformed into the δ and fluorite phases by the rearrangement of the oxygen vacancies.

DOI： 10.1016/j.jeurceramsoc.2023.12.063

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Metastable Substitution of an Isovalent Anion Element in SnSe Films to Control the Thermoelectric Property 査読有り

Yamaguchi K., Ishimaru M., Horide T.

ACS Applied Electronic Materials 6 ( 2 ) 1071 - 1077 2024年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

To improve the thermoelectric properties of SnSe films, carrier control is required, but elemental doping is difficult due to the thermodynamic solubility limit. Isovalent elements may generate holes or electrons not in a direct manner but in the manner to form point defects. In this study, the Sn(Se,Te) films were fabricated by a pulsed laser deposition (PLD) method to control the carrier concentration by substituting isovalent Te for Se. The coexistence of the orthorhombic and cubic phases at the tens of nanometer scale in the SnSe0.5Te0.5 film was clarified by the structural observation, which is consistent with the equilibrium phase diagram. In spite of the phase coexistence, the lattice parameters linearly increased with an increase in the Te content in the Sn(Se,Te) films. This demonstrates the metastable composition situation for each phase, namely, the carrier control beyond the thermodynamic limit due to the nonequilibrium growth in PLD. As a result, the Seebeck coefficient decreased, and the electrical conductivity increased to increase the power factor, especially in a low temperature near room temperature. The Te substitution in the nonequilibrium PLD increases the hole concentration beyond the thermodynamic solubility limit and thus is effective in controlling the carrier in the SnSe films where carrier doping is difficult.

DOI： 10.1021/acsaelm.3c01490

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Carrier Control of Bi-Doped SnSe Films for Fabrication of π-Type Thermoelectric Film Modules 査読有り国際誌

Horide T., Nakamura K., Ishimaru M.

ACS Applied Energy Materials 7 ( 1 ) 346 - 352 2024年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Thermoelectric energy conversion is promising for high-efficiency power generation. The p- and n-type thermoelectric materials are required to fabricate high-performance thermoelectric modules. SnSe is one of the highest-performance thermoelectric materials, and SnSe films should be fabricated for small-scale applications. While the p-type SnSe films can be easily prepared without precise control of the doping, it is difficult to control the electron concentration in the n-type SnSe films. In this study, the Bi-doped SnSe films were fabricated at low deposition temperatures by using the self-buffer layer, namely, the SnSe-based buffer layers. The low-temperature deposition on the buffer layer increased the concentration of doped Bi, although the contribution of the buffer layer to the electronic conduction was observed. The π-type thermoelectric module consisting of p-type SnSe and n-type SnSe/buffer layers was fabricated. The output power of 0.09 μW and the open-circuit voltage of 0.11 V were obtained at 155 °C at the cold end and 255 °C at the hot end. The feasibility of fabricating the π-type SnSe film module was demonstrated. By optimizing the buffer layer thickness and increasing the number of legs, we expect the module performance to be further improved.

DOI： 10.1021/acsaem.3c02683

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アモルファス炭化ホウ素の電子線動径分布解析招待有り査読有り

石丸学

表面と真空 ( 公益社団法人日本表面真空学会 ) 66 ( 12 ) 719 - 724 2023年12月

担当区分：筆頭著者,　最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）

<p>Short-range and medium-range ordered structures of amorphous materials can be evaluated by radial distribution functions and atomic pair-distribution functions extracted by quantitative analyses of diffraction intensities. Because of the strong interaction of electrons with materials and the short wavelength of high-energy electrons, electron diffraction can produce intensity profiles up to high scattering angles comparable to those of neutron diffraction and synchrotron x-ray diffraction in a short time. Here, we present an example of electron diffraction radial distribution function analysis of amorphous boron carbide by electron diffraction techniques.</p>

DOI： 10.1380/vss.66.719

その他リンク： https://www.jstage.jst.go.jp/article/vss/66/12/66_20181187/_pdf

Modulation of vortex pinning by matrix defects in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf>nanocomposite film 査読有り

Horide T., Higashi K., Ishimaru M., Okada T., Awaji S., Matsumoto K.

Superconductor Science and Technology 36 ( 10 ) 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Nanorods are a very effective pinning center in YBa2Cu3O7 films, and the vortex pinning mechanism should be understood to further improve the critical current density (J c) in the nanocomposite films. Matrix defects are naturally formed during nanocomposite growth, and in this study the effect of matrix defects on the J c in the YBa2Cu3O7 films containing nanorods is discussed. YBa2Cu3O7 + BaHfO3 and YBa2Cu3O7 + BaSnO3 films were prepared by varying the laser repetition frequency to control the matrix defects. All the films contained the nanorods. The YBa2Cu3O7 + BaHfO3 film of 2 Hz exhibits high J c for magnetic field parallel to the c-axis (B//c) due to the nanorods and the isolated random point defects. In the YBa2Cu3O7 + BaHfO3 film of 10 Hz, while the short stacking faults and networked random point defects decreased the J c for B//c, the short stacking faults improved the J c for tilted magnetic field. In the YBa2Cu3O7 + BaSnO3 film of 10 Hz, the isolated random point defects improved J c regardless of the magnetic field direction. While the ab-plane correlated defects are analyzed by the structural observation, the network or isolated nature of the random point defects can be discussed by the normal state resistivity. The matrix defects of YBa2Cu3O7 nanocomposite films should be designed considering the correlated/network/isolated nature which is determined by the morphology and defect concentration.

DOI： 10.1088/1361-6668/acecad

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85169547502&origin=inward

Nano- to microscale structural and compositional heterogeneity of artificial pinning centers in pulsed-laser-deposited YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7−y</inf> thin films 査読有り

Kuroki M., Horide T., Matsumoto K., Ishimaru M.

Journal of Applied Physics 134 ( 4 ) 2023年07月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The structure, composition, and spatial distribution heterogeneity of artificial pinning centers affect the critical current density of REBa2Cu3O7−y (RE: rare earth) coated conductors. Nanoscale structures and compositions have been analyzed with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). However, microscale heterogeneity has been difficult to characterize. Here, YBa2Cu3O7−y thin films doped with double-perovskite Ba2YbNbO6 were prepared via pulsed-laser deposition and characterized with TEM, STEM, and scanning electron microscopy (SEM). Cross-sectional and plan-view TEM/STEM imaging revealed hybrid pinning structures consisting of nanorods, nanoparticles, and planar defects that were formed spontaneously. Nanorods were imaged with high spatial resolution via field-emission SEM of thin-foil specimens. Focused-ion-beam (FIB) micro-sectioning enables SEM imaging of microscale heterogeneity in nanorod spatial distributions. By using TEM/STEM in conjunction with FIB-SEM, the coated conductor inhomogeneity was directly evaluated from the nano- to micrometer scales.

DOI： 10.1063/5.0155145

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85166486407&origin=inward

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