Article
Physics, Applied
Yutaka Ohno, Takehiro Tamaoka, Hideto Yoshida, Yasuo Shimizu, Kentaro Kutsukake, Yasuyoshi Nagai, Noritaka Usami
Summary: Research shows that non-coherent sigma 3{111} grain boundaries with a positive tilt angle deviation exhibit high recombination activity in high-performance multicrystalline silicon ingots. The presence of edge-type dislocations with a specific Burgers vector arrangement, along with stretched 110 reconstructed bonds to prevent dangling bonds, leads to the generation of large strains around dislocation cores. This strain-induced segregation of oxygen and carbon atoms is believed to be the main cause of the recombination activity.
APPLIED PHYSICS EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Q. Barres, O. Tissot, E. Meslin, I. Mouton, B. Arnal, M. Loyer-Prost, C. Pareige
Summary: Investigated the effect of grain boundary variations on radiation-induced segregation in Ferritic Martensitic and ODS steels. Quantified the structural characteristics and chemical composition of grain boundaries using multiple techniques. Results showed W-shaped profiles of Cr across grain boundaries and heterogeneous precipitation of Cr-C rich particles on grain boundary planes.
MATERIALS CHARACTERIZATION
(2022)
Article
Chemistry, Physical
Song Wang, Yi Kong, Li Chen, Yong Du
Summary: In this study, the effect of twelve <110> symmetric tilt grain boundaries (GBs) on the initial oxidation behavior of TiN was investigated using first-principles calculation method. It was found that Sigma 3 (111) GB has an extremely small energy, while other GBs have high energies. The oxygen adsorption results showed that GBs are chemically more favorable sites for oxygen, and Sigma 3 (111) GB can enhance the oxidation resistance of TiN. Additionally, Si doping can further improve the oxidation resistance of TiN with Sigma 3 (111) GB.
SURFACES AND INTERFACES
(2023)
Article
Materials Science, Multidisciplinary
Ken-ichi Ebihara, Tomoaki Suzudo
Summary: The migration of phosphorus atoms in different types of grain boundaries differs, which is crucial for understanding the phenomenon of grain boundary phosphorus segregation.
Article
Nanoscience & Nanotechnology
Jonathan D. Poplawsky, Rishi Pillai, Qing-Qiang Ren, Andrew J. Breen, Baptiste Gault, Michael P. Brady
Summary: Understanding the oxygen solubility in materials is crucial for designing oxidation resistant alloys. Atom Probe Tomography (APT) provides high chemical sensitivity and resolution, revealing the oxygen content within Ni metal and grain boundaries.
SCRIPTA MATERIALIA
(2022)
Article
Nanoscience & Nanotechnology
Seiichiro Ii, Takero Enami, Takahito Ohmura, Sadahiro Tsurekawa
Summary: TEM in situ straining was used to investigate the slip behavior at grain boundaries in an aluminum bicrystal. The shear stress required for dislocation transfer at the grain boundary was evaluated and it was found that the activated slip system in the adjacent grain is primarily controlled by local energetic and geometric conditions.
SCRIPTA MATERIALIA
(2022)
Article
Materials Science, Multidisciplinary
Nannan Chen, Haris Ali Khan, Shenxi Li, Jingjing Li
Summary: This study investigated the mechanisms behind the increased electrical conductivity in pure copper joined with aluminum via micro friction stir blind riveted and post-heating. The increase in E3 boundaries and reduction in random grain boundaries were identified as the main contributing factors. While this grain boundary engineering approach led to improved electrical conductivity, high-temperature heating resulted in a significant reduction in microhardness due to strain relief and grain growth.
MATERIALS CHARACTERIZATION
(2021)
Article
Materials Science, Multidisciplinary
Shengli Guo, Xiaoyu Zhang, Jun Zhong, Shuaishuai Wu, Wei Jiang
Summary: In this study, the deviation distributions of Sigma 3 and Sigma 9 grain boundaries in a Hastelloy C-276 sheet were measured using EBSD technology. The results showed that the hot rolling process caused significant deviation of Sigma 3 grain boundary orientations and loss of special properties. On the other hand, the Sigma 9 grain boundary plane distribution became more diffused with increasing deformation. Additionally, distorted grain boundaries acted as nucleation sites for dynamic recrystallization during hot rolling.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Chemistry, Physical
Ivan Lobzenko, Yoshinori Shiihara, Yoshitaka Umeno, Yoshikazu Todaka
Summary: Nanocrystallization processes can enhance the tribological properties of metallic surfaces under boundary lubrication conditions. Adsorption of fatty lubricant molecules on a nanostructured iron surface was found to be stronger near grain boundaries, as revealed by first-principles calculations.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Hongtao Xue, Yaqiao Luo, Fuling Tang, Xuefeng Yu, Xuefeng Lu, Junqiang Ren
Summary: GBSE is a promising approach for accurately manipulating the chemical composition, structure, and properties of grain boundaries. Through investigating the segregation behaviors of transition metal solutes in nickel-based superalloy grain boundaries, it is found that most solutes can reduce grain boundary energy and increase stability and fracture strength. The study provides insights into designing nickel-based superalloys with improved performance.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Nanoscience & Nanotechnology
Yuanxiang Zhang, Guo Yuan, Yang Wang, Feng Fang, Weina Zhang, Xiaoming Zhang, Guodong Wang
Summary: A novel high magnetic induction Fe-6.5%Si alloy was prepared by twin-roll strip casting, with a B-800 reaching up to 1.77 Telsa. The formation of Sigma 3 grain boundaries and their inheritance from the rolling and annealing processes stabilized the matrix grain boundaries, resulting in the formation of a perfect Goss microstructure with excellent magnetic properties.
SCRIPTA MATERIALIA
(2021)
Article
Nuclear Science & Technology
Xiao-yu Zhang, Jun Zhong, Sheng-li Guo, Jun Zhao
Summary: Reasonable deformation and annealing treatment parameters lead to more incoherent Sigma 3 boundaries playing an important role in the optimization of GBE.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Metallurgy & Metallurgical Engineering
YiFan Li, JianBo Lin, JinXu Li, Shigenobu Ogata, WenTong Geng
Summary: Experimental evidence suggests that sigma 3(111) twin boundaries in austenitic steels are prone to hydrogen embrittlement. Despite this, first-principles calculations show that these twin boundaries are not trapping sites for hydrogen. Density functional theory calculations of interlayer distances and hydrogen solution energies near the sigma 3(111) twin boundary in gamma-iron reveal oscillating behavior due to Friedel oscillations. The presence of Friedel oscillations near the twin boundary drives hydrogen accumulation, potentially contributing to hydrogen embrittlement near the boundaries.
STEEL RESEARCH INTERNATIONAL
(2022)
Article
Physics, Condensed Matter
Rita Maji, Julia Contreras-Garcia, Eleonora Luppi, Elena Degoli
Summary: Grain boundaries in multicrystalline silicon interacting with inherent defects and impurity elements play a decisive role in their electrical behavior, with strain playing an important role in these systems. The distribution of strain and the number of impurity atoms are observed to modify the energetics of the material. However, the electronic properties of the considered Si-GBs are not significantly affected by strain and oxygen impurities unless high local distortion induces additional structural defects.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2022)
Article
Geochemistry & Geophysics
Tommaso Tacchetto, Steven M. Reddy, David W. Saxey, Denis Fougerouse, William D. A. Rickard, Chris Clark
Summary: Characterization of deformation-related low-angle boundaries in olivine reveals preferential segregation of trace elements to these interfaces, likely associated with subgrain rotation recrystallization and dislocation migration. This phenomenon has significant implications for understanding olivine deformation at mantle depth and the redistribution of elements deep in the Earth.
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
(2021)
Article
Physics, Applied
Jianbo Liang, Daiki Takatsuki, Masataka Higashiwaki, Yasuo Shimizu, Yutaka Ohno, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: In this work, Ga2O3(001)/Si(100) and Ga2O3(010)/Si(100) heterointerfaces were fabricated through surface activated bonding at room temperature. The thermal stability of the heterointerfaces was investigated by heating the bonding samples at different temperatures and it was found that the heterointerface with a thin Si exhibited good thermal stability at 1000 degrees C. An intermediate layer was formed at both heterointerfaces, with the Ga2O3(001)/Si(100) heterointerface having a uniform thickness while the Ga2O3(010)/Si(100) heterointerface having a non-uniform thickness.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Jiao Chen, Kenta Yoshida, Tomoaki Suzudo, Yusuke Shimada, Koji Inoue, Toyohiko J. Konno, Yasuyoshi Nagai
Summary: In situ electron irradiation was used to study the evolution of Frank loops in an aluminum-copper alloy. The experiments showed an asymmetrical climb of the Frank loops under electron irradiation, which was not observed in pure aluminum. Theoretical calculations and molecular dynamics simulations suggested that the Cu-Cu bonding in Guinier-Preston zones could act as a pinning site for the dislocation climb.
MATERIALS TRANSACTIONS
(2022)
Article
Physics, Applied
Ryo Kagawa, Keisuke Kawamura, Yoshiki Sakaida, Sumito Ouchi, Hiroki Uratani, Yasuo Shimizu, Yutaka Ohno, Yasuyoshi Nagai, Jianbo Liang, Naoteru Shigekawa
Summary: We have successfully fabricated AlGaN/GaN high electron mobility transistors (HEMTs) on diamond substrates, and found that the HEMTs on diamond have smaller negative drain conductance due to their lower thermal resistance. This implies that the bonding-first process is applicable for fabricating HEMTs with low thermal resistance and thick nitride layers.
APPLIED PHYSICS EXPRESS
(2022)
Article
Physics, Applied
Yutaka Ohno, Jianbo Liang, Hideto Yoshida, Yasuo Shimizu, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: The chemical composition around diamond/silicon heterointerfaces fabricated through surface activated bonding (SAB) at room temperature was examined. Iron impurities were found to segregate at the bonding interfaces, while oxygen impurities were found to segregate off the bonding interfaces in the silicon side. When the bonding interfaces were annealed, the amorphous compound converted to cubic silicon carbide (c-SiC) and nano-voids were formed between silicon and c-SiC. These nano-voids acted as sites for metal impurities to agglomerate and helped to improve the electronic properties of the bonding interfaces through impurity gettering.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Takumi Deshimaru, Kenta Yamakoshi, Kentaro Kutsukake, Takuto Kojima, Tsubasa Umehara, Haruhiko Udono, Noritaka Usami
Summary: The growth mechanism of multicrystalline Mg2Si crystal was analyzed using optical reflection image analysis and crystal orientation measurement. It was found that grains with higher surface energy competitively expanded during crystal growth, possibly due to the difference in growth rate caused by high supercooling.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Jing Wang, Yuji Hatano, Takeshi Toyama, Tatsuya Hinoki, Kiyohiro Yabuuchi, Yi-fan Zhang, Bing Ma, Alexander V. Spitsyn, Nikolay P. Bobyr, Koji Inoue, Yasuyoshi Nagai
Summary: This study systematically investigates the irradiation responses of binary W alloys, focusing on the binding energy of an alloying element with a W self-interstitial atom (W-SIA). Plates of W, W-0.3 at.% Cr, W-5 at.% Re, W-2.5 at.% Mo, and W-5 at.% Ta alloys were irradiated, and the formation of vacancy-type defects, the precipitation of alloying elements, and the changes in hardness were studied. It was found that the addition of Cr and Re effectively suppresses the formation of vacancy-type defects, while Ta and Mo have no significant suppression effect. Irradiation hardening was observed in all materials, but its degree was smaller in the W-5 at.% Re alloy.
MATERIALS & DESIGN
(2023)
Article
Nuclear Science & Technology
Lei Zhang, Yufeng Du, Wentuo Han, Xiaoou Yi, Pingping Liu, Kenta Yoshida, Takeshi Toyama, Chi Xu, Qian Zhan, Yasuyoshi Nagai, Somei Ohnuki, Farong Wan
Summary: Due to reduced activation, the severe radioactivity of tantalum (Ta) after neutron irradiation is easily ignored. This study found that a RAFM steel specimen with a small weight of 0.8 g had drastic radioactivity of 4 mSv/hour at a measuring distance of 20 cm after an irradiation of only 0.3 dpa and a cooling stage of 305 days. It was determined that the high radioactivity was caused by 182Ta. The increased danger of material experiments calls for serious consideration of the radioactivity of Ta and control of its content in RAFM steel.
NUCLEAR MATERIALS AND ENERGY
(2023)
Article
Multidisciplinary Sciences
Rikuya Sato, Kentaro Kutsukake, Shunta Harada, Miho Tagawa, Toru Ujihara
Summary: Technology computer-aided design (TCAD) simulation is a valuable tool for semiconductor device development. However, the increasing complexity and miniaturization of devices have resulted in longer calculation times. This study proposes a neural network architecture that uses machine learning to speed up TCAD simulations by considering the structure of the coupled partial differential equations. The method is evaluated using a simulation dataset and shows promising advantages compared to conventional neural network models. It can be applied to other physics problems described by coupled PDEs and has the potential to accelerate simulations in various fields.
ADVANCED THEORY AND SIMULATIONS
(2023)
Article
Physics, Applied
Kazuki Sawai, Jianbo Liang, Yasuo Shimizu, Yutaka Ohno, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: The electrical properties of group-III nitride heterojunctions are greatly affected by interface charges due to polarizations discontinuity. Ga-face/Ga-face and N-face/N-face interfaces with antiparallel spontaneous polarizations were fabricated using surface-activated bonding of double-side polished freestanding GaN (0001) wafers to investigate their electrical and nanostructural properties. After annealing at 600 degrees C, the built-in potential of the N-face/N-face interface is smaller than that of the Ga-face/Ga-face interface. The difference in built-in potentials between the two antiparallel polarized interfaces is analyzed using a charge-neutrality-level model and the density of interface states is roughly estimated. The leakage in both Ga-face/Ga-face and N-face/N-face interfaces is enhanced at higher annealing temperatures, suggesting the contribution of defects near the bonding interfaces.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Kenta Yamakoshi, Yutaka Ohno, Kentaro Kutsukake, Takuto Kojima, Tatsuya Yokoi, Hideto Yoshida, Hiroyuki Tanaka, Xin Liu, Hiroaki Kudo, Noritaka Usami
Summary: A comprehensive analysis of optical and photoluminescence images from multicrystalline silicon wafers is conducted using machine learning models, resulting in the establishment of a realistic 3D model that includes the generation point of dislocation clusters. The study reveals the mechanism of dislocation generation and its importance in materials science.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Ryo Kagawa, Zhe Cheng, Keisuke Kawamura, Yutaka Ohno, Chiharu Moriyama, Yoshiki Sakaida, Sumito Ouchi, Hiroki Uratani, Koji Inoue, Yasuyoshi Nagai, Naoteru Shigekawa, Jianbo Liang
Summary: This study demonstrates the potential of fabricating GaN HEMTs on diamond substrates by successfully transferring AlGaN/GaN/3C-SiC layers to large diamond substrates and maintaining the integrity and high thermal conductivity of the substrate interface. It enables high-quality crystal growth and excellent heat dissipation performance.
Article
Materials Science, Multidisciplinary
Yuya Hattori, Shunsuke Yoshizawa, Keisuke Sagisaka, Yuki Tokumoto, Keiichi Edagawa, Takako Konoike, Shinya Uji, Taichi Terashima
Summary: Scanning tunneling microscopy and transport measurements were used to investigate the electronic structure and temperature dependence in heavily Sr and Na codoped PbTe. The band gap increases with doping, leading to band convergence, which is desirable for thermoelectric materials. At higher temperatures, carrier redistribution occurs between different bands.
