Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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Application of Bayesian Super-Resolution to Spectroscopic Data for Precise Characterization of Spectral Peak Shape Reviewed Open Access

Kota Tsujimori, Jun Hirotani, Shunta Harada

JOURNAL OF ELECTRONIC MATERIALS Vol. 51 ( 2 ) page： 712 - 717 2022.2

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

The number of data points of digitally recorded spectra have been limited by the number of multichannel detectors employed, which sometimes impedes the precise characterization of spectral peak shape. Here we describe a methodology to increase the number of data points as well as the signal-to-noise (S/N) ratio by applying Bayesian super-resolution in the analysis of spectroscopic data. In our present method, first, the hyperparameters for the Bayesian super-resolution are determined by a virtual experiment imitating actual experimental data, and the precision of the super-resolution reconstruction is confirmed by the calculation of errors from the ideal values. For validation of the super-resolution reconstruction of spectroscopic data, we applied this method to the analysis of Raman spectra. From 200 Raman spectra of a reference Si substrate with a data interval of about 0.8 cm(-1), super-resolution reconstruction with a data interval of 0.01 cm(-1) was successfully achieved with the promised precision. From the super-resolution spectrum, the Raman scattering peak of the reference Si substrate was estimated as 520.55 (+0.12, -0.09) cm(-1), which is comparable to the precisely determined value reported in previous works. The present methodology can be applied to various kinds of spectroscopic analysis, leading to increased precision in the analysis of spectroscopic data and the ability to detect slight differences in spectral peak positions and shapes.

DOI： 10.1007/s11664-021-09326-4

Open Access

Web of Science

Scopus

Solvent design aiming at solution property induced surface stability: A case study using SiC solution growth Reviewed

Xinbo Liu, Yifan Dang, Koki Suzuki, Can Zhu, Wancheng Yu, Shunta Harada, Miho Tagawa, Toru Ujihara

JOURNAL OF CRYSTAL GROWTH Vol. 578 page： 126425 2022.1

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

For solution growth of silicon carbide, it is significant to understanding the evolutionary mechanism of step bunching. This study infers that solute's incorporation into steps and transport together determines step bunching progress. The occurrence of step bunching is due to the depletion of solute in the region with high step density, caused by a high step kinetic coefficient. On the other hand, by promoting the transport of the solute in the solution, the step speed becomes uniform, thereby the step bunching can be prevented. Furthermore, we proposed a non-dimensional Damko center dot hler number for crystal growth in step-flow mode. It correlates incorporation rates with bulk diffusion rates and can build a phase map of growth rates and step bunching stability. Several solvents are located in the phase map, demonstrating the possible usage of the phase map as a pointer for solvent designing.

DOI： 10.1016/j.jcrysgro.2021.126425

Web of Science

Scopus

Automatic Detection of Basal Plane Dislocations in a 150-mm SiC Epitaxial Wafer by Photoluminescence Imaging and Template-matching Algorithm Reviewed

Shunta Harada, Kota Tsujimori, Yosuke Matsushita

JOURNAL OF ELECTRONIC MATERIALS Vol. 51 ( 1 ) page： 243 - 248 2022.1

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

In this study, an algorithm was constructed for the automatic detection of basal plane dislocations (BPDs) propagating in SiC epitaxial layers in photoluminescence images, and its performance was evaluated. The BPDs are the origin of the degradation of SiC bipolar devices caused by the expansion of stacking faults. The present automatic detection algorithm, based on the template-matching method, was confirmed to have high accuracy and precision, and we succeeded in visualizing the BPD density in 150-mm SiC epitaxial wafers. We confirmed that the template-matching method is applicable for the detection of crystalline defects with geometrically fixed shapes such as BPDs in SiC epitaxial layers.

DOI： 10.1007/s11664-021-09284-x

Web of Science

Scopus

High fracture toughness AlN achieved by addition of AlN whiskers and tape-casting Reviewed Open Access

Hiroki Shimizu, Naoki Kondo, Akihiro Shimamura, Mikinori Hotta, Shunta Harada, Toru Ujihara, Yoshihiro Ohnishi

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 130 ( 1 ) page： 195 - 198 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Aluminum nitride (AlN) possesses excellent thermal conductivity and electrical resistivity, which makes it an ideal candidate for high-power, high-speed integrated circuit substrates. Its low fracture toughness requires the manufacturing of thicker substrates. However, this leads to degraded heat dissipation performance. Herein, we investigated a new strategy, combining the addition of AlN whiskers and tape-casting, to overcome the low fracture toughness disadvantage. The sintered AlN with AlN whiskers addition induced the formation of a highly anisotropic microstructure with aligned rod-like grains, effectively enhancing the fracture toughness to 6.7 MPa m1/2, while maintaining thermal conductivity but degrading strength. (c) 2022 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.21143

Polarized light observation of semiconductor wafers for power devices

Murayama K., Mizutani S., Mizutani Y., Harada S.

2022 IEEE International Meeting for Future of Electron Devices, Kansai, IMFEDK 2022 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：2022 IEEE International Meeting for Future of Electron Devices, Kansai, IMFEDK 2022

Polarized light observation is one of the promising methods for the non-destructive characterization of semiconductor wafers for power devices. We have visualized the distribution of defects in SiC wafers by birefringence imaging.

DOI： 10.1109/IMFEDK56875.2022.9975432

Scopus

Process informatics using simulation data for crystal growth

Kutsukake Kentaro, Tsunooka Yosuke, Wancheng Yu, Dang Yifan, Harada Shunta, Ujihara Toru

Journal of the Japanese Association for Crystal Growth Vol. 49 ( 1 ) page： n/a 2022

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Association for Crystal Growth

<p> In this paper, machine learning and optimization based on simulation data of crystal growth are discussed from the viewpoint of informatics application, introducing our application to solution growth of SiC crystal. First, general aspects of crystal growth process simulation and its informatics applications are described. Next, after an overview of the solution growth of SiC crystal, the process optimization of solution growth of SiC crystal using machine learning is described, including the prediction model of temperature and flow of the solution in the crucible, the optimization of geometry conditions, and the optimization of process conditions corresponding to time evolution. Next, application to other materials is described. Finally, this paper is summarized with future prospects.</p>

DOI： 10.19009/jjacg.49-1-06

CiNii Research

Association between Achilles Tendon Softness and Atherosclerotic Cardiovascular Disease in Patients with Familial Hypercholesterolemia

Michikura, M; Ogura, M; Hori, M; Matsuki, K; Makino, H; Hosoda, K; Harada-Shiba, M

JOURNAL OF ATHEROSCLEROSIS AND THROMBOSIS Vol. 29 ( 11 ) page： 1603 - 1612 2022

Immobilization of partial dislocations bounding double Shockley stacking faults in 4H-SiC observed by in situ synchrotron X-ray topography Reviewed

Fumihiro Fujie, Shunta Harada, Hiromasa Suo, Balaji Raghothamachar, Michael Dudley, Kenji Hanada, Haruhiko Koizumi, Tomohisa Kato, Miho Tagawa, Toru Ujihara

MATERIALIA Vol. 20 page： 101246 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9 x 10(19) cm(-3) was investigated using in situ synchrotron X-ray topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by non-conservative motion induced by the interaction between the PDs and point defects (C interstitials).

DOI： 10.1016/j.mtla.2021.101246

Web of Science

Scopus

Surface relaxation and photoelectric absorption effects on synchrotron X-ray topographic images of dislocations lying on the basal plane in off-axis 4H-SiC crystals Reviewed Open Access

Tuerxun Ailihumaer, Hongyu Peng, Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Shunta Harada, Toru Ujihara

Materials Science and Engineering B: Solid-State Materials for Advanced Technology Vol. 271 page： 115281 2021.9

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

A more sophisticated simulation model is developed based on the principle of ray-tracing to simulate the grazing-incidence synchrotron X-ray topographic contrast of dislocations lying on the basal plane including basal plane dislocations and deflected threading screw and mixed dislocations in off-axis 4H-SiC crystals. The model incorporates effects of surface relaxation as well as the photoelectric absorption to predict dislocation contrast. Compared to conventional ray-tracing images, surface relaxation effects dominate dislocation contrast for diffraction near the crystal surface. The simulated dislocation contrast gradually weakens with increasing depth of the diffracted beam position within the crystal due to photoelectric absorption. The distinctive features of the net simulated dislocation images obtained by aggregating through the effective penetration depth correlate well with contrast features observed on the experimental topographic images. Depth analysis reveals that in some cases the diffracted X-rays from regions below the dislocation can contribute additional contrast features previously not considered.

DOI： 10.1016/j.mseb.2021.115281

Web of Science

Scopus

Estimation of melt state dynamics in floating zone method using Gaussian mixture model

Omae Ryo, Sumitani Shogo, Tosa Yusuke, Harada Shunta

JSAP Annual Meetings Extended Abstracts Vol. 2021.2 ( 0 ) page： 3410 - 3410 2021.8

Two-Step Nanoparticle Crystallization via DNA-Guided Self-Assembly and the Nonequilibrium Dehydration Process Reviewed Open Access

Hayato Sumi, Noboru Ohta, Hiroshi Sekiguchi, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto, Miho Tagawa

Crystal Growth and Design Vol. 21 ( 8 ) page： 4506 - 4515 2021.8

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

DNA strands are powerful tools as ligand molecules that bind nanoparticles to each other via programmable self-assembly for colloidal crystallization. We found that hydrated DNA-functionalized nanoparticle (DNA-NP) superlattices with a properly controlled volume fraction and spatial arrangement of nanoparticles successfully maintained their crystallinity even after dehydration, which involves drastic contraction. A detailed study of the structural changes was performed for the self-assembled DNA-NP sample using small-angle X-ray scattering (SAXS) after dehydration. Then, an optimal volume fraction of nanoparticles in the superlattice, φ, which minimized the level of distortion of the dehydrated superlattice, was found for each bcc and fcc structure. By acquiring clear SAXS diffraction patterns showing crystal symmetries for dehydrated DNA-NP superlattices, their lattice distortion was evaluated using our analysis technique, which is based on Hosemann's paracrystalline theory and involves SAXS and scanning electron microscopy data. Geometrical calculations substantiated the ease of movement of a nanoparticle under the influence of repulsions from adjacent particles that mainly affect the dehydration stability. These results suggest that it is possible to design the crystal structure of solid nanoparticle superlattices via DNA-guided nanoparticle assembly under a near-equilibrium state in solution as the first step, followed by dehydration under nonequilibrium conditions as the second step.

DOI： 10.1021/acs.cgd.1c00398

Open Access

Web of Science

Scopus

Local Atomic Structures for Tunable Ordered Arrangements of Crystallographic Shear Planes in Titanium-Chromium Oxide Natural Superlattices Reviewed

Shunta Harada, Shunya Sugimoto, Naoki Kosaka, Miho Tagawa, Toru Ujihara

Journal of Physical Chemistry C Vol. 125 ( 28 ) page： 15730 - 15736 2021.7

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The atomic structure of titanium-chromium oxide natural superlattices with different compositions having an ordered arrangement of crystallographic shear (CS) planes was investigated by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and electron diffraction, using polycrystalline ceramics prepared by arc-melting and heat treatment. Analysis of the electron diffraction patterns revealed that not only the interspacing but also the direction of planar faults changed depending on the chromium concentration. HAADF-STEM observations showed that the atomic arrangements of CS planes deviating from (121)rutile are random arrangements of (121)rutile CS planes and (011)rutile antiphase boundaries. Using a random walk model and by calculating the specularity parameter, we found that the CS planes in titanium-chromium oxides behave as coherent interfaces for phonons based on the estimation of interface roughness.

DOI： 10.1021/acs.jpcc.1c04516

Web of Science

Scopus

Ordered Arrangement of Planar Faults with Picoscale Perfection in Titanium Oxide Natural Superlattices Reviewed

S. Harada, N. Kosaka, M. Tagawa, T. Ujihara

The Journal of Physical Chemistry C Vol. 125 ( 20 ) page： 11175 - 11181 2021.5

Design of automatic detection algorithm for dislocation contrasts in birefringence images of SiC wafers Reviewed

Kawata Akira, Murayama Kenta, Sumitani Shogo, Harada Shunta

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( SB ) 2021.5

Synchrotron X-ray topographic image contrast variation of screw-type basal plane dislocations located at different depths below the crystal surface in 4H-SiC Reviewed International coauthorship

Fujie Fumihiro, Peng Hongyu, Ailihumaer Tuerxun, Raghothamachar Balaji, Dudley Michael, Harada Shunta, Tagawa Miho, Ujihara Toru

ACTA MATERIALIA Vol. 208 2021.4

Geometrical design of a crystal growth system guided by a amachine learning algorithm Reviewed

Wancheng Yu, Can Zhu, Wei Huang, Dang Yifan, Kentaro Kutsukake, Shunta Harada, Miho Tagawa, Toru Ujihara

CrystEngComm Vol. 23 ( 14 ) page： 2695 - 2702 2021.4

Adaptive process control for crystal growth using machine learning for high-speed prediction: application to SiC solution growth

Dang Yifan, Zhu Can, Ikumi Motoki, Takaishi Masaki, Yu Wancheng, Huang Wei, Liu Xinbo, Kutsukake Kentaro, Harada Shunta, Tagawa Miho, Ujihara Toru

CrystEngComm Vol. 23 ( 9 ) page： 1982 - 1990 2021.3

Analysis of dislocation line tilt in GaN single crystal by Raman spectroscopy

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( SA ) 2021.1

Technologies for large-diameter SiC crystal growth and application of process informatics

Ujihara Toru, Zhu Can, Tsunooka Yosuke, Furusho Tomoaki, Suzuki Koki, Kutsukake Kentaro, Takaishi Masaki, Yu Wancheng, Dang Yifan, Isono Masaru, Takeuchi Ichiro, Tagawa Miho, Harada Shunta

Journal of the Japanese Association for Crystal Growth Vol. 48 ( 3 ) page： n/a 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Association for Crystal Growth

<p> We have been developing a SiC crystal growth technique using the solution method. As a result, we have achieved the growth of ultra-high quality crystals with extremely low dislocation density. The key to this is the reduction of dislocation density by utilizing the macro-step dislocation conversion phenomenon and the suppression of surface morphology roughness by controlling the flow in the solution. In order to put these technologies to practical use, we have developed a new machine learning technique for optimizing crystal growth conditions for large-diameter crystals. In this method, a model is constructed in the computer that reproduces the actual experiment quickly and accurately, and then hundreds of thousands or millions of trials are performed using the model to derive the experimental conditions with high efficiency. This means that optimization by surrogate models, which is one of the methods of process informatics, has been realized in crystal growth. By using these techniques, we were able to achieve 6-inch crystal growth in a very short time.</p>

DOI： 10.19009/jjacg.48-3-04

CiNii Research

Numerical investigation and optimization of time evolution in the solution during solution growth for SiC crystal

Dang Yifan, Zhu Can, Yu Wancheng, Huang Wei, Ikumi Motoki, Harada Shunta, Tagawa Miho, Ujihara Toru

JSAP Annual Meetings Extended Abstracts Vol. 2020.2 ( 0 ) page： 2128 - 2128 2020.8

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Papers - HARADA Shunta