Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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Ultrahigh-resolution direct observation of mini-bands formed in InGaAs/AlGaAs superlattice

Shimura Daiki, Ichihashi Fumiaki, Nishitani Kenji, Harada Shunta, Kuwahara Makoto, Ito Takahiro, Matsunami Masaharu, Kimura Shin-ichi, Sakai Takenobu, Tagawa Miho, Ujihara Toru

2013 IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC) page： 306 - 310 2013

2SBA-03 DNA-mediated Nanoparticle Assembly(2SBA Reconstitution of life phenomena in a designed reaction field : Synthetic biology approach to Biophysics,Symposium,The 51th Annual Meeting of the Biophysical Society of Japan)

Tagawa Miho, Isogai Takumi, Akada Eri, Harada Syunta, Ujihara Toru, Yanger Kevin, Gang Oleg

Seibutsu Butsuri Vol. 53 ( 1 ) page： S92 2013

Polytype-selective growth of SiC by supersaturation control in solution growth

Kazuaki Seki, Alexander, Shigeta Kozawa, Shunta Harada, Toru Ujihara, Yoshikazu Takeda

JOURNAL OF CRYSTAL GROWTH Vol. 360 ( 1 ) page： 176 - 180 2012.12

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

We realized the polytype-selective growth of 3C-SiC and 6H-SiC on a 6H-SiC (0 0 0 1) seed crystal by controlling the supersaturation. Both 6H-SiC and 3C-SiC grew on the 6H-SiC seed crystal at low supersaturation, but 3C-SiC increased with increasing supersaturation. At high supersaturation, 3C-SiC grew so rapidly that it completely covered the 6H-SiC seed crystal. The growth rates of 3C-SiC and 6H-SiC have different dependences on supersaturation. In the present case, the growth rate of 3C-SiC in 2D nucleation mode is compared with that of 6H-SiC in spiral growth mode. The present kinetic polytype-control technique is based on polytypes having different growth rates and it differs considerably from the conventional technique that is based on "inheritance" of stacking sequence, which is well known as "step-controlled epitaxy". (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2011.11.041

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Scopus

High-Efficiency Conversion of Threading Screw Dislocations in 4H-SiC by Solution Growth

YAMAMOTO Yuji, HARADA Shunta, SEKI Kazuaki, HORIO Atsushi, MITSUHASHI Takato, UJIHARA Toru

Applied physics express : APEX Vol. 5 ( 11 ) page： "115501 - 1"-"115501-3" 2012.11

High-Efficiency Conversion of Threading Screw Dislocations in 4H-SiC by Solution Growth Reviewed

Yuji Yamamoto, Shunta Harada, Kazuaki Seki, Atsushi Horio, Takato Mitsuhashi, Toru Ujihara

APPLIED PHYSICS EXPRESS Vol. 5 ( 11 ) page： 115501 2012.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The high-efficiency conversion of threading screw dislocations (TSDs) in 4H-SiC by solution growth provides an efficient method of obtaining ultra high-quality SiC crystals. The behavior of TSDs on on-axis and off-axis 4H-SiC{0001} seed crystals was investigated by synchrotron X-ray topography. Almost all TSDs in the off-axis Si-face seed crystal were converted to Frank-type stacking faults on the basal planes. The conversion ratio of TSDs was highly influenced by the surface polarity of the seed crystal. The stacking faults laterally propagate toward the outside of the crystal. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/APEX.5.115501

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Polytype Transformation by Replication of Stacking Faults Formed by Two-Dimensional Nucleation on Spiral Steps during SiC Solution Growth Reviewed

Shunta Harada, Alexander, Kazuaki Seki, Yuji Yamamoto, Can Zhu, Yuta Yamamoto, Shigeo Arai, Jun Yamasaki, Nobuo Tanaka, Toru Ujihara

CRYSTAL GROWTH & DESIGN Vol. 12 ( 6 ) page： 3209 - 3214 2012.6

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

Polytype transformations on the 4H-SiC(0001) Si face during top-seeded solution growth have been investigated by transmission electron microscopy and micro-Raman spectroscopy. 4H-, 15R-, and 6H-SiC were grown on the 4H-SiC(0001) Si face via spiral growth. Once a polytype transformation from 4H-SiC to 15R- or 6H-SiC occurs, the polytype rarely returns to 4H-SiC. Just before the polytype transformation, a disturbance in the stacking sequence involving the introduction of stacking faults was observed. A polytype transformation during spiral growth can be understood in terms of the replication of stacking faults due to two-dimensional nucleation of a single bilayer on the spiral steps. This polytype transformation model shows good agreement with observed polytype transformation pathways as well as the disturbance in the stacking sequence at the interface between 4H-SiC and 15R-SiC.

DOI： 10.1021/cg300360h

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Scopus

Stable Growth of 4H-SiC Single Polytype by Controlling the Surface Morphology Using a Temperature Gradient in Solution Growth Reviewed

Y. Yamamoto, K. Seki, S. Kozawa, Alexander, S. Harada, T. Ujihara

Materials Science Forum Vol. 717-720 page： 53-56 2012.5

Anisotropy of Lattice Thermal Conduction in TiO2-x with High Density of Planar Defects by Atomistic Simulations

Y. Miyauchi, M. Tada, M. Yoshiya, S. Harada, K. Tanaka, H. Yasuda, H. Inui

AMTC Letters Vol. 3 page： 242-243 2012.5

Conversion Mechanism of Threading Screw Dislocation during SiC Solution Growth

T. Ujihara, S. Kozawa, K. Seki, Alexander, Y. Yamamoto, S. Harada

Materials Science Forum Vol. 717-720 page： 351-354 2012.5

Anisotropy of Lattice Thermal Conduction in TiO2-x with High Density of Planar Defects by Atomistic Simulations

Y. Miyauchi, M. Tada, M. Yoshiya, S. Harada, K. Tanaka, H. Yasuda, H. Inui

AMTC Letters Vol. 3 page： 242-243 2012.5

CT-2-2 Solution Growth of High-Quality SiC Crystal

Ujihara Toru, Harada Shunta, Seki Kazuaki, Yamamoto Yuji

Proceedings of the IEICE General Conference Vol. 2012 ( 2 ) page： "SS - 19"-"SS-21" 2012.3

CT-2-2 Solution Growth of High-Quality SiC Crystal

Ujihara Toru, Harada Shunta, Seki Kazuaki, Yamamoto Yuji

Proceedings of the IEICE General Conference Vol. 2012 ( 2 ) page： "SS - 19"-"SS-21" 2012.3

Direct Observation of Vacancies and Local Thermal Vibration in Thermoelectric Rhenium Silicide Reviewed

Shunta Harada, Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto, Noriaki Endo, Eiji Okunishi, Haruyuki Inui

APPLIED PHYSICS EXPRESS Vol. 5 ( 3 ) page： 035203 2012.3

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

The crystal structure of rhenium silicide with an anomalous ordered arrangement of vacancies has been investigated by utilizing spherical-aberration (C-s)-corrected scanning transmission electron microscopy (STEM). Using C-s-corrected STEM imaging, we directly observe for the first time ordered silicon vacancies in thermoelectric rhenium silicide accompanied by anomalously large local thermal vibration ("rattling" motion) of silicon atoms in their adjacent sites. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/APEX.5.035203

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Scopus

Conversion Mechanism of Threading Screw Dislocation during SiC Solution Growth

Toru Ujihara, Shigeta Kozawa, Kazuaki Seki, Alexander, Yuji Yamamoto, Shunta Harada

SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2 Vol. 717-720 page： 351 - + 2012

Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

Solution growth is considered to be a powerful method for high quality SiC crystals. This work reports that the conversion process from a threading screw dislocation into a few Frank partial dislocations in basal planes was investigated by synchrotron X-ray topography. This process was effectively assisted by step-flow growth on off-oriented (0001) seed crystals. The Frank partials were not extended into the crystal grown toward the [0001] direction perpendicular to the basal plane. Thus, the conclusion of this study suggests the use of off-orientcd seed crystal is important to improve crystal quality.

DOI： 10.4028/www.scientific.net/MSF.717-720.351

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Stable Growth of 4H-SiC Single Polytype by Controlling the Surface Morphology Using a Temperature Gradient in Solution Growth Reviewed

Yuji Yamamoto, Kazuaki Seki, Shigeta Kozawa, Alexander, Shunta Harada, Toru Ujihara

SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2 Vol. 717-720 page： 53 - 56 2012

Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD

We introduce a method to grow 4H-SiC single polytype stably by controlling the surface morphology. The polytype transition on on-axis 4H-SiC C-face was investigated from a viewpoint of surface morphology of grown layers. At the area where several hillock-like structures grew adjacently, the polytype transition from 4H-SiC to 6H-SiC or 15R-SiC often occurred. Therefore, we tried a vertical seeded solution growth (VSSG) method to suppress the formation of hillock-like structures. As a result, the hillock-like structure on the grown layer was dramatically reduced. Moreover, the ratio of 4H-SiC polytype to the whole grown surface was increased to be almost 100%.

DOI： 10.4028/www.scientific.net/MSF.717-720.53

Web of Science

Scopus

Acoustic Design Shape and Topology Sensitivity Formulations Based on Adjoint Method and BEM

Matsumoto, T; Yamada, T; Takahashi, T; Zheng, CJ; Harada, S

CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES Vol. 78 ( 2 ) page： 77 - 94 2011.8

Crystal structure refinement of ReSi1.75 with an ordered arrangement of silicon vacancies Reviewed

Shunta Harada, Hiroaki Hoshikawa, Kosuke Kuwabara, Katsushi Tanaka, Eiji Okunishi, Haruyuki Inui

PHILOSOPHICAL MAGAZINE Vol. 91 ( 23 ) page： 3108 - 3127 2011

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

The crystal structure and microstructure of ReSi1.75 were investigated by synchrotron X-ray diffraction combined with scanning transmission electron microscopy. ReSi1.75 contains an ordered arrangement of vacancies in Si sites in the underlying tetragonal C11(b) lattice of the MoSi2-type and the crystal structure is monoclinic with the space group Cm. Atomic positions of Si atoms near vacancies are considerably displaced from the corresponding positions in the parent C11(b) structure, and they exhibit anomalously large local thermal vibration accompanied by large values of atomic displacement parameter. There are four differently-oriented domains with two of them being related to each other by the 90 degrees rotation about the c-axis of the underlying C11(b) lattice and the other two being their respective twins. The habit planes for domain boundaries observed experimentally are consistent with those predicted with ferroelastic theory.

DOI： 10.1080/14786435.2011.570278

Web of Science

Scopus

Direct observation of an ordered arrangement of vacancies and large local thermal vibration in rhenium silicide by Cs-corrected STEM Reviewed

Shunta Harada', Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto', Noriaki Endo, Eiji Okunishi, Haruyuki Inui

Materials Research Society Symposium Proceedings Vol. 1295 page： 397 - 402 2011

Language：English Publishing type：Research paper (international conference proceedings)

The crystal structure of thermoelectric rhenium silicide with an ordered arrangement of vacancies is investigated by utilizing spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM) combined with synchrotron X-ray diffraction and conventional transmission electron microscopy. By STEM Cs corrected imaging, we can clearly observe Si vacancies in rhenium silicide, which is impossible without Cs correction. In addition, significantly reduced contrast levels are noted in STEM images for particular Si sites near vacancies. From the STEM image simulation, the reduced contrast levels are concluded to be due to anomalously large local thermal vibration of these Si atoms. The crystal structure of rhenium silicide can be successfully refined by the synchrotron X-ray diffraction starting with the deduced structure model from the STEM images and the occurrence of large local thermal vibration can be qualitatively confirmed. Furthermore, we confirm the validity of the refined crystal structure of rhenium silicide by comparing experimental images with simulated image generating with the refined crystal structure parameters. © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.43

Scopus

Formation mechanism of high-density AlN by the nitridation of molten Al

Mizuno Kohei, Matubara Hiroaki, Takeuchi Yukihisa, Harada Shunta, Ujihara Toru, Aoki Yuuichi, Kohara Kimio

Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan Vol. 2011 ( 0 ) page： 761 - 761 2011

Atomic-level analyses of thermal conduction in magneli-phase TiO<sub>2-x</sub> containing shear structure

Yoshiya Masato, Miyauchi Yohei, Tada Masahiro, Harada Shunta, Tanaka Katsushi, Yasuda Hideyuki, Inui Haruyuki

Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan Vol. 2011 ( 0 ) page： 759 - 759 2011

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Papers - HARADA Shunta