Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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Machine learning for SiC top-seeded solution growth - Prediction, optimization and visualization

Ujihara T.

CS MANTECH 2019 - 2019 International Conference on Compound Semiconductor Manufacturing Technology, Digest of Papers 2019

Evaluation of basal plane dislocation behavior in the epitaxial layer on a 4H-SiC wafer fabricated by the solution growth method

Seki K.

Materials Science Forum Vol. 963 MSF page： 80 - 84 2019

The Prediction Model of Crystal Growth Simulation Built by Machine Learning and Its Applications

UJIHARA Toru, TSUNOOKA Yosuke, HATASA Goki, KUTSUKAKE Kentaro, ISHIGURO Akio, MURAYAMA Kenta, NARUMI Taka, HARADA Shunta, TAGAWA Miho

Vacuum and Surface Science Vol. 62 ( 3 ) page： 136 - 140 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Vacuum and Surface Science

<p>The prediction model of the result of computed fluid dynamics simulation in SiC solution growth was constructed on neural network using machine learning. Utilizing the prediction model, we can optimize quickly crystal growth conditions. In addition, the real-time visualization system was also made using the prediction model.</p>

DOI： 10.1380/vss.62.136

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CiNii Research

The relationships between crystal orientation and morphology of electrode from a perspective of crystal growth

Ishikawa Kohei, Mitsuhashi Takato, Ito Yasumasa, Takeuchi Yukihisa, Harada Shunta, Tagawa Miho, Ujihara Toru

Journal of the Japanese Association for Crystal Growth Vol. 46 ( 1 ) page： 136-140 2019

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

<p> Metal anodes are promising materials for rechargeable batteries because of the higher capacity. However, low cycle efficiency due to non-uniform deposition prevents them from realization. In this review, we report the crystal orientation dependence of the deposition shape of Li and Zn, which are known as attractive materials for anodes. The result shows that the both of Li and Zn morphology has crystal orientation dependence.</p>

DOI： 10.19009/jjacg.46-1-08

Improvement mechanism of sputtered AlN films by high-temperature annealing

Shiyu Xiao, Ryoya Suzuki, Hideto Miyake, Shunta Harada, Toru Ujihara

Journal of Crystal Growth Vol. 502 page： 41 - 44 2018.11

High-speed prediction of computational fluid dynamics simulation in crystal growth

Tsunooka Yosuke, Kokubo Nobuhiko, Hatasa Goki, Harada Shunta, Tagawa Miho, Ujihara Toru

CRYSTENGCOMM Vol. 20 ( 41 ) page： 6546 - 6550 2018.11

Determination of edge-component Burgers vector of threading dislocations in GaN crystal by using Raman mapping

Kokubo Nobuhiko, Tsunooka Yosuke, Fujie Fumihiro, Ohara Junji, Onda Shoichi, Yamada Hisashi, Shimizu Mitsuaki, Harada Shunta, Tagawa Miho, Ujihara Toru

APPLIED PHYSICS EXPRESS Vol. 11 ( 11 ) 2018.11

Observation of carrier recombination in single Shockley stacking faults and at partial dislocations in 4H-SiC

Kato Masashi, Katahira Shinya, Ichikawa Yoshihito, Harada Shunta, Kimoto Tsunenobu

JOURNAL OF APPLIED PHYSICS Vol. 124 ( 9 ) 2018.9

Classification and behavior of dislocations propagating from GaN substrate to epitaxial film

Inotsume Sho, Kokubo Nobuhiko, Yamada Hisashi, Onda Shoichi, Ohara Junji, Harada Shunta, Tagawa Miho, Ujihara Toru

JSAP Annual Meetings Extended Abstracts Vol. 2018.2 ( 0 ) page： 3248 - 3248 2018.9

In Situ Observation of Chiral Symmetry Breaking in NaClO3 Chiral Crystallization Realized by Thermoplasmonic Micro-Stirring

Niinomi Hiromasa, Sugiyama Teruki, Tagawa Miho, Harada Shunta, Ujihara Tom, Uda Satoshi, Miyamoto Katsuhiko, Omatsu Takashige

CRYSTAL GROWTH & DESIGN Vol. 18 ( 8 ) page： 4230 - 4239 2018.8

Direct observation of stacking fault shrinkage in 4H-SiC at high temperatures by in-situ X-ray topography using monochromatic synchrotron radiation

Fujie Fumihiro, Harada Shunta, Koizumi Haruhiko, Murayama Kenta, Hanada Kenji, Tagawa Miho, Ujihara Toru

APPLIED PHYSICS LETTERS Vol. 113 ( 1 ) 2018.7

Development of angle-resolved spectroscopy system of electrons emitted from a surface with negative electron affinity state

Ichihashi Fumiaki, Dong Xinyu, Inoue Akito, Kawaguchi Takahiko, Kuwahara Makoto, Ito Takahiro, Harada Shunta, Tagawa Miho, Ujihara Toru

REVIEW OF SCIENTIFIC INSTRUMENTS Vol. 89 ( 7 ) 2018.7

Detection of edge component of threading dislocations in GaN by Raman spectroscopy

Nobuhiko Kokubo, Yosuke Tsunooka, Fumihiro Fujie, Junji Ohara, Kazukuni Hara, Shoichi Onda, Hisashi Yamada, Mitsuaki Shimizu, Shunta Harada, Miho Tagawa, Toru Ujihara

Applied Physics Express Vol. 11 ( 6 ) 2018.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Applied Physics

We succeeded in measuring the density and direction of the edge component of threading dislocations (TDs) in c-plane (0001) GaN by micro- Raman spectroscopy mapping. In the micro-Raman spectroscopy mapping of the E2 H peak shift between 567.85 and 567.75 cm-1, six different contrast images are observed toward directions of h1-100i. By comparing X-ray topography and etch pit images, the E2 H peak shift is observed where the edge component of TDs exists. In contrast, the E2 H peak is not observed where the screw component of TDs exists.

DOI： 10.7567/APEX.11.061002

Web of Science

Scopus

Dislocation behavior in bulk crystals grown by TSSG method

Kazuaki Seki, Kazuhiko Kusunoki, Yutaka Kishida, Hiroshi Kaido, Koji Moriguchi, Motohisa Kado, Hironori Daikoku, Takayuki Shirai, Mitsutoshi Akita, Akinori Seki, Hiroaki Saito, Shunta Harada, Toru Ujihara

Materials Science Forum Vol. 924 page： 39 - 42 2018

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

The dislocation behavior during bulk crystal growth on the 4H-SiC (000-1) C-face using the solution method was investigated. A 2 inch wafer with a 4 degree off angle was fabricated from a bulk crystal grown by the TSSG method, and the dislocations in the crystal were evaluated using synchrotron X-ray topography and TEM observation. From the topograph images, it was found that the TSD density remarkably decreased as the growth progressed. Furthermore, the TEM observation suggested that TSD decreases as the threading dislocations convert to in-plane defects toward the center of the crystal. Conventionally, it was considered that conversion of threading dislocations hardly occurs in solution growth on the C-face. However, it is thought that this phenomenon was not observable because the conversion efficiency is remarkably low. We speculate that dislocations may be converted by suddenly making macrosteps during bulk growth.

DOI： 10.4028/www.scientific.net/MSF.924.39

Scopus

Suppression of polytype transformation with extremely low-dislocation-density 4H-SiC crystal in two-step solution method

Kenta Murayama, Shunta Harada, Fumihiro Fujie, Xin Bo Liu, Ryota Murai, Can Zhu, Kenji Hanada, Miho Tagawa, Toru Ujihara

Materials Science Forum Vol. 924 page： 60 - 63 2018

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

We achieved the growth of extremely-high quality SiC crystal with two-step solution method with specially-designed seed crystals. The two-step growth consists of 1st step growth on Si-face for the reduction of threading dislocations and 2nd step growth on C-face for the reduction of basal plane dislocations and thickening. In this method, we can make the dislocation density extremely low, while the polytype easily changes during growth due to the absence of spiral hillocks originating from threading screw dislocation (TSD). In this study, we prepared specially designed seed crystals for both 1st and 2nd growth steps to provide steps continuously. In the seeds, a few TSDs exist at the upper-side of the step structure. Consequently, we demonstrated the suppression of the polytype transformation during the C-face growth with extremely low-dislocation-density crystal. Accordingly, we successfully obtained extremely low-dislocation density 4H-SiC with TSD, TED and BPD density of 11, 385 and 28 cm-2.

DOI： 10.4028/www.scientific.net/MSF.924.60

Scopus

Temperature dependence of carrier relaxation time in gallium phosphide evaluated by photoemission measurements

Fumiaki Ichihashi, Takahiko Kawaguchi, Xinyu Dong, Makoto Kuwahara, Takahiro Ito, Shunta Harada, Miho Tagawa, Toru Ujihara

AIP ADVANCES Vol. 7 ( 11 ) 2017.11

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

For understanding of carrier behavior in semiconductors, it is important to measure the carrier relaxation time. In the present study, the relaxation times of inter-valley transition from the valley to the X valley in GaP were evaluated by near-band-gap photoemission spectroscopy of electrons emitted from a surface with a negative electron affinity state. In the energy distribution curves, two peaks, which originate from the electron population accumulated in the valley and the X valley, were observed. From the temperature dependence of the energy of these two peaks, we could successfully evaluate the temperature dependence of the energies of the valley and the X valley. Furthermore, the relaxation times of the inter-valley transition from the valley to the X valley were estimated from the ratio of the electron concentration of the valley and the X valley. The values of the relaxation time are good agreement with the previous studies. These results indicate that the near-band-gap photoemission spectroscopy can directly investigate conduction electrons and also evaluate the carrier dynamics in semiconductor. (C) 2017 Author(s).

DOI： 10.1063/1.4997800

Web of Science

Scopus

Optimization of crystallization conditions of SiC crystal with machine learning

Murai Ryota, Hatasa Goki, Tunooka Yosuke, Lin Hung, Murayama Kenta, Zhu Can, Harada Shunta, Tagawa Miho, Ujihara Toru

JSAP Annual Meetings Extended Abstracts Vol. 2017.2 ( 0 ) page： 3506 - 3506 2017.8

Investigation of high-temperature annealing process of sputtered AlN films

Xiao Shiyu, Liu Yikang, Suzuki Ryoya, Miyake Hideto, Hiramatsu Kazumasa, Harada Shunta, Ujihara Toru

JSAP Annual Meetings Extended Abstracts Vol. 2017.2 ( 0 ) page： 3378 - 3378 2017.8

Phase transition process in DDAB supported lipid bilayer

Takumi Isogai, Sakiko Nakada, Naoya Yoshida, Hayato Sumi, Ryugo Tero, Shunta Harada, Toru Ujihara, Miho Tagawa

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 88 - 92 2017.6

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

We report the results of microscope measurements examining the phase transition process of a cationic lipid, Dimethyldioctadecylammonium bromide (DDAB) supported lipid bilayer (SLB). Due to lateral fluidity and strong electrostatic interaction with DNA, SLB serves as a fluid substrate for assembling 2D lattices of DNA functionalized nanoparticles (DNA-NPs): lipid molecules work as carriers for transporting DNA-NPs. By fluorescence microscopy and atomic force microscopy (AFM), two types of phase transitions, which correspond to liquid crystalline-gel and liquid crystalline-interdigitated gel (L beta I) ones, were observed in DDAB SLB during cooling. In thermal equilibrium at room temperature both gel and L beta I phases have enough adsorbed amounts of DNA-NPs which indicate that both domains have enough surface charge densities for adsorbing DNA-NPs, however, during phase transition DNA-NPs preferably distributed into L beta I phase.

DOI： 10.1016/j.jcrysgro.2016.09.063

Web of Science

Scopus

Morphology of AlN whiskers grown by reacting N-2 gas and Al vapor

M. Matsumoto, H. Saitou, Y. Takeuchi, S. Harada, M. Tagawa, T. Ujihara

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 576 - 580 2017.6

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

We have investigated the morphology of AlN whiskers on a polycrystalline AlN substrate by using Fe-Al alloy melts under the different synthesis conditions. Formation density of the AlN whiskers increases and the diameter of the whisker decreases with increasing Al content of the Fe-Al alloy melt. Most of the AlN whiskers were zigzag shape with the hexagonal cross section. The longitudinal direction was the [0001] direction. The facet with the zigzag shape was the {1101} or {1101} pyramidal plane and the period of the zigzag facet was almost constant. The average diameter of the whiskers and the period of the zigzag facet decrease with increasing Al content. At the initial stage of the whisker formation, the island of AlN formed on the AlN substrate and the pyramidal facet grows via step-flow growth. From the observation, we discussed the possible mechanism for the formation of the zigzag-shape AlN whiskers.

DOI： 10.1016/j.jcrysgro.2016.11.127

Web of Science

Scopus

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Papers - HARADA Shunta