Article
Materials Science, Multidisciplinary
Zixiang Yan, Qiang Yang, Fanzhi Meng, Rui Ma, Rirong Bao, Xiaojuan Liu, Jian Meng, Xin Qiu
Summary: In this study, interfacial precipitation in {10 (1) over bar2} twin boundaries of a cold-stamped Mg-12Gd-1.2Zn-0.4Zr alloy was investigated, revealing the formation of new interfacial phases which accelerated peak-aging and improved the alloy's strength. This periodic segregation of Gd + Zn atoms in the twin boundaries played a crucial role in enhancing the mechanical properties of the alloy.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2021)
Article
Nanoscience & Nanotechnology
Hu Zhao, Halil Yilmaz, Craig J. Williams, Alexander S. Eggeman, Brian Derby
Summary: The study compares the tensile mechanical properties of silver nanowires produced by different methods and finds a significant size effect in the plastic flow strengths of both sets of nanowires, where smaller diameters result in higher strengths. Similar deformation structures and low dislocation densities were observed in both classes of nanowires studied.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Materials Science, Multidisciplinary
Wei Li, Benjia Zhu, Mathias Uller Rothmann, Amelia Liu, Weijian Chen, Yen Yee Choo, Narendra Pai, Wenxin Mao, Tian Zhang, Qiaoliang Bao, Xiaoming Wen, Udo Bach, Joanne Etheridge, Yi-Bing Cheng
Summary: The study demonstrates that halide segregation and I-V hysteresis in mixed halide inorganic CsPbIBr2 solar cells can be effectively mitigated by introducing an intermediate phase-enhanced Ostwald ripening through the control of chemical composition in the precursor solution. By adjusting the stoichiometric ratios of PbBr2 and CsI, improved solar cell performance can be achieved, with excess lead phase promoting Ostwald maturation and defect extinction. Ultimately, the CsPbIBr2 solar cell with a PbBr2-excess precursor composition achieves a high power conversion efficiency and external quantum efficiency.
SCIENCE CHINA-MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Zongde Kou, Tao Feng, Si Lan, Song Tang, Lixia Yang, Yanqing Yang, Gerhard Wilde
Summary: Through in situ tensile experiments, it was found that dislocations can be transported by twin lamella via periodic twinning and detwinning, revealing a novel evolution route of dislocations through dislocation-twin interaction.
Article
Nanoscience & Nanotechnology
T. W. J. Kwok, T. P. McAuliffe, A. K. Ackerman, B. H. Savitzky, M. Danaie, C. Ophus, D. Dye
Summary: A TWIP steel with a specific composition was deformed to 6% strain and analyzed using 4D-STEM technique. It was found that the average elastic strain parallel and perpendicular to the twinning direction was about 6%, but there were hot spots with even larger strains up to 12%. These hot spots were attributed to a high density of Frank dislocations on the twin boundary. The strain fields in the TWIP steel were significantly larger than other twinning materials, and could explain the early thickness saturation of nanotwins.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Chemistry, Multidisciplinary
Penghui Li, Yeqiang Bu, Linyan Wang, Chong Wang, Junquan Huang, Ke Tong, Yujun Chen, Julong He, Zhisheng Zhao, Bo Xu, Zhongyuan Liu, Guoying Gao, Anmin Nie, Hongtao Wang, Yongjun Tian
Summary: Fracture behaviors in perfect and twinned B4C crystals were studied via in situ TEM mechanical testing. It was found that cracks preferentially initiated at the twin boundaries (TBs) and propagated along them, resulting in the fracture of B4C. The theoretical calculations also showed a softening effect of TBs on B4C, with amorphous bands preferentially nucleated at the TBs. These findings clarify the atomic arrangement and the role of planar defects in the failure of B4C.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Xuexi Yan, Yixiao Jiang, Bing Yang, Shangyi Ma, Tingting Yao, Ang Tao, Chunlin Chen, Xiuliang Ma, Hengqiang Ye
Summary: Diamond thin films have great potential for electronic and microwave applications as wide band gap semiconductor materials. This study investigates the impact of twin boundaries on the band gap of diamond and reveals that the band gap can be tuned by strain engineering. The findings have significant implications for the innovation and design of advanced diamond functional devices.
Article
Chemistry, Physical
Binting Huang, Jishi Yang, Zhiheng Luo, Yang Wang, Nan Wang
Summary: The rapid solidification process often leads to high-density microstructure defects and residual thermal stress in metals. Twin boundaries, which are potentially beneficial, have been observed in rapidly solidified nanocrystalline microstructures. This study proposes a pathway for forming twin boundaries and provides a detailed derivation of strain inhomogeneities and the deformation twinning phase field method. By calculating the cooling-induced thermal strain inhomogeneity and growth thresholds for deformation twinning, it is shown that residual thermal strain hotspots in the microstructure can reach the threshold for deformation twinning when there is a significant difference in shear elastic property between grain boundaries and the bulk material.
Article
Chemistry, Physical
Nicolas J. Peter, Daniela Zander, Xumeng Cao, Chunhua Tian, Siyuan Zhang, Kui Du, Christina Scheu, Gerhard Dehm
Summary: This study reports the observation of enhanced oxygen diffusion along crystal defects, specifically dislocations and twin boundaries, in the C15 Al2Ca Laves phase. The presence of oxygen induces structural changes in these defects, leading to the formation of an amorphous oxide. The identification of oxygen-induced transformation at strained defects is important when the material is exposed to air during plastic deformation at elevated temperatures. Rating: 8/10.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Microscopy
Michael Stoeger-Pollach, Keanu Zenz, Felix Ursin, Johannes Schilberg, Leo Stoeger
Summary: Cathodoluminescence (CL) is a developing analytical method in electron microscopy due to its excellent energy resolution. A Czerny-Turner type spectrometer with a blazed grating as analyzer is usually used. Unlike a prism analyzer, the grating has a linear spectral distribution. However, higher-order refraction affects the measured optical spectrum at larger wavelengths. This study presents a method for correcting the acquired optical spectra by considering higher order diffraction intensities.
Article
Materials Science, Multidisciplinary
Andriy Ostapovets, Konstantin Kushnir, Kristian Mathis, Filip Siska
Summary: Both types of obstacles inhibit twin growth and require increased stress to engulf them. However, the increase of critical resolved shear stress is higher for the interaction with a row of voids compared to non-shearable obstacles.
Article
Materials Science, Multidisciplinary
Shujuan Wang, Khanh Dang, Rodney J. McCabe, Laurent Capolungo, Carlos N. Tome
Summary: A comprehensive study explored the facets that bound the compression twin in Ti, observing six new facets and validating the results through HRTEM observations and atomistic simulations. The new facets align with low-index interfaces, with those having lower surface energies forming extended interfaces, while higher surface energy facets are located at the twin tip region. These findings provide a better understanding of the 3D structure of compression twins in Ti and validate the MD procedure and Ti interatomic potential used in the study.
Article
Nanoscience & Nanotechnology
Zhiqiao Li, Houwen Chen, Jian-Feng Nie
Summary: In this work, the migrations of (1011) and (1013) coherent twin boundaries (CTB) in pure magnesium are studied using first-principles methods. The process of migration is divided into nucleation and gliding of twinning disconnection (TD), with TD nucleation approximated by rigid-shifting of CTB. Energetic maps obtained from this analysis reveal the necessity of applying shear strains simultaneously along the twinning direction η1 and along k1, which is normal to η1, to activate the migration of 2-layer CTB in these two different twinning modes. The energetic map identifies the most efficient external shear strain direction for initiating CTB migration, which lies between the Burgers vectors bTD-2 of the 2-layer-height TD and η1. The shear strain required to initiate TD gliding is smaller than that needed for TD nucleation, implying that the migrations of (1011) and (1013) CTBs are primarily governed by the TD nucleation.
SCRIPTA MATERIALIA
(2023)
Article
Chemistry, Multidisciplinary
Hikaru Saito, Daichi Yoshimoto, Yuto Moritake, Taeko Matsukata, Naoki Yamamoto, Takumi Sannomiya
Summary: Using gap surface plasmons for high index contrasting, a wide-bandgap valley plasmonic crystal has been achieved for waveguiding in the near-infrared-visible range, providing a practical platform for transferring angular momentum between photons and carriers.
Article
Chemistry, Multidisciplinary
Kyohei Yamagata, Matsuhiro Maeda, Zeno Tessari, Kunal S. Mali, Yoshito Tobe, Steven De Feyter, Kazukuni Tahara
Summary: Grain boundaries in polycrystals significantly affect material properties, leading to research on grain boundary engineering. Using scanning tunneling microscopy, the authors observed quasi-periodic nanoscale chirality switching and twinning in self-assembled molecular networks at the liquid/solid interface. The width of the chiral domain structure peaked at 12-19 nm, and adjacent domains were connected through interdigitated alkoxy chains, forming a defect-free domain border.
Article
Materials Science, Multidisciplinary
Jianbo Liang, Yuji Nakamura, Tianzhuo Zhan, Yutaka Ohno, Yasuo Shimizu, Kazu Katayama, Takanobu Watanabe, Hideto Yoshida, Yasuyoshi Nagai, Hongxing Wang, Makoto Kasu, Naoteru Shigekawa
Summary: Direct integration of GaAs and diamond was achieved at room temperature via surface activated bonding, forming an ultrathin crystal defect layer. GaAs TLM patterns on diamond substrates demonstrated excellent heat dissipation properties due to the high thermal conductivity of diamond.
DIAMOND AND RELATED MATERIALS
(2021)
Article
Physics, Applied
Yutaka Ohno, Jie Ren, Shingo Tanaka, Masanori Kohyama, Koji Inoue, Yasuo Shimizu, Yasuyoshi Nagai, Hideto Yoshida
Summary: Through the use of atom probe tomography combined with a focused ion beam operated at -150 degrees C, the three-dimensional distribution of oxygen atoms segregated at sigma 9{114} grain boundaries in Czochralski-grown silicon ingots was analyzed with high spatial resolution. The analysis revealed a narrow segregation range of oxygen atoms across the grain boundary plane, with segregation sites existing at bond-centered sites under tensile stresses above 2 GPa, as calculated by ab initio local stress calculations.
APPLIED PHYSICS EXPRESS
(2021)
Article
Chemistry, Multidisciplinary
Jianbo Liang, Ayaka Kobayashi, Yasuo Shimizu, Yutaka Ohno, Seong-Woo Kim, Koji Koyama, Makoto Kasu, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: The direct integration of GaN and diamond for high-power devices faces challenges due to mismatch in lattice and thermal-expansion coefficients. A successful fabrication of GaN/diamond heterointerface was achieved using a surface activated bonding method at room temperature. An intermediate layer composed of amorphous carbon and diamond is formed at the interface, with Ga and N atoms diffusing during the bonding process and transitioning to diamond after annealing.
ADVANCED MATERIALS
(2021)
Article
Crystallography
Yutaka Ohno, Tomio Kajigaya, Kazutaka Osako, Toshio Kochiya
Summary: The cracking process of 36-degree RY lithium tantalate (LiTaO3) single crystals during Czochralski (CZ) growth was examined. It was found that twin lamellae were generated beneath the -Z' surface of the ingots due to the dissociation of dislocations composing the lineages. Cracking occurred at the intersections where the twin lamellae grew with the CZ growth towards the bottom of the ingots.
JOURNAL OF CRYSTAL GROWTH
(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
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
Yusuke Fukuda, Kentaro Kutsukake, Takuto Kojima, Yutaka Ohno, Noritaka Usami
Summary: This study investigates the effects of grain boundary structures on the carrier recombination velocity in multicrystalline silicon. The results show that the deviation angle from the ingot growth direction has a relatively large impact on the carrier recombination velocity. Additionally, it is found that grain boundaries with lower energy have lower carrier recombination velocity.
JOURNAL OF APPLIED PHYSICS
(2022)
Review
Physics, Applied
Naoteru Shigekawa, Jianbo Liang, Yutaka Ohno
Summary: Recent achievements in the research of heterojunctions fabricated using surface activated bonding (SAB) technology are discussed in this paper, with a focus on the response of bonding interfaces to post-bonding annealing. The study reveals that defect layers formed at the bonded interfaces can be improved and the heterojunctions exhibit high thermal tolerance. Characteristics of III-V//Si multijunction solar cells, GaN-on-diamond high electron mobility transistors, and metal-foil based low-loss interconnects that are fabricated by processing SAB-based junctions are described, along with future prospects.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Multidisciplinary Sciences
Zhe Cheng, Jianbo Liang, Keisuke Kawamura, Hao Zhou, Hidetoshi Asamura, Hiroki Uratani, Janak Tiwari, Samuel Graham, Yutaka Ohno, Yasuyoshi Nagai, Tianli Feng, Naoteru Shigekawa, David G. Cahill
Summary: In this study, the authors report isotropic high thermal conductivity of 3C-SiC wafers exceeding 500 W m(-1)K(-1). The material not only has high thermal conductivity, but also provides important insights into fundamental phonon transport mechanisms, making it an excellent material for next-generation power electronics.
NATURE COMMUNICATIONS
(2022)
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
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
Crystallography
Yutaka Ohno, Yuta Kubouchi, Hideto Yoshida, Toshio Kochiya, Tomio Kajigaya
