Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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Thin film growth of CaFe2As2 by molecular beam epitaxy Reviewed

T. Hatano, T. Kawaguchi, R. Fujimoto, I. Nakamura, Y. Mori, S. Harada, T. Ujihara and H. Ikuta

Superconductor Science and Technology Vol. 29 page： 015013 2015

Measurement of Energy Distribution of Conduction Electrons in Superlattice by Visible-Light Photoemission Spectroscopy

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

2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) 2015

Measurement of Energy Distribution of Conduction Electrons in Superlattice by Visible-Light Photoemission Spectroscopy Reviewed

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

2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) 2015

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

Visible-light photoemission spectroscopy (VPS) is a novel angle-resolved photoemission spectroscopy developed by us for measuring conduction electrons emitted from a surface with negative electron affinity state. In this study, InGaAs/GaAsP quantum well superlattice was analyzed by the VPS method with changing the excitation photon energy. By comparing with comparison of the energy distribution curves obtained by different excitation energy, the first and second conduction mini-band structures were directly clarified.

Web of Science

Dislocation Conversion during SiC Solution Growth for High-quality Crystals Reviewed

原田俊太

Materials Forum Vol. N/A 2015

Different behavior of threading edge dislocation conversion during the solution growth of 4H-SiC depending on the Burgers vector

Shunta Harada, Yuji Yamamoto, Kazuaki Seki, Atsushi Horio, Miho Tagawa, Toru Ujihara

ACTA MATERIALIA Vol. 81 page： 284 - 290 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Threading edge dislocation (TED) conversion during the solution growth of SiC was investigated by synchrotron X-ray topography. TEDs were converted to basal plane dislocations by lateral growth with the advance of macrosteps on the growth surface during the solution growth. TEDs with the Burgers vector parallel to the step-flow direction were converted to basal plane dislocations with a high probability. On the other hand, the conversion ratio of TEDs whose Burgers vector is not parallel to the step-flow direction was much lower. The variation in elastic energy of the basal plane dislocations after the conversion depending on the Burgers vectors led to the different behavior of TED conversion. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2014.08.027

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Scopus

Electrostatic acceleration of helicon plasma using a cusped magnetic field

Harada S., Baba T., Uchigashima A., Yokota S., Iwakawa A., Sasoh A., Yamazaki T., Shimizu H.

APPLIED PHYSICS LETTERS Vol. 105 ( 19 ) 2014.11

Forming two-dimensional structure of DNA-functionalized Au nanoparticles via lipid diffusion in supported lipid bilayers

Takumi Isogai, Agnes Piednoir, Eri Akada, Yuki Akahoshi, Ryugo Tero, Shunta Harada, Toru Ujihara, Miho Tagawa

JOURNAL OF CRYSTAL GROWTH Vol. 401 page： 494 - 498 2014.9

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

Two-dimensional (2D) form of DNA-functionalized gold nanoparticles (DNA-AuNPs) has been studied. To confine the DNA-AuNPs in 2D space, we utilized the strong affinity between DNA molecules and supported lipid bilayers (SLBs). DNA-AuNPs adsorbed onto cationic SLB consisting of Dimethyl dioctadecyl ammonium bromide (DDAB) on mica substrate with high affinity. Owing to the high mobility of lipid molecules, 2D diffusion and transportation of DNA-AuNPs on the SLB was achieved. Using AFM imaging we confirmed a selective adsorption of DNA-AuNPs onto cationic lipid bilayer patches on mica surface, and then we confirmed a drastic formation change of DNA-AuNPs on the SLB with annealing. We observed that the DNA-AuNPs assembled into a densely packed single layered 2D superstructure through DNA hybridization. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2014.01.032

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Scopus

The investigation of step structure with different TSDs conversion behavior during 4H-SiC solution growth

Xiao Shiyu, Hara Natsumi, Harada Shunta, Ujihara Toru

JSAP Annual Meetings Extended Abstracts Vol. 2014.2 ( 0 ) page： 3317 - 3317 2014.9

Defect evolution in high-quality 4H-SiC grown by solution method

Harada, S; Tagawa, M; Ujihara, T

ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES Vol. 70 page： C1415 - C1415 2014.8

Defect evolution in high-quality 4H-SiC grown by solution method

Harada S, Tagawa M, Ujihara T

ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES Vol. 70 page： C1415 - C1415 2014.8

Emergence and Amplification of Chirality via Achiral-Chiral Polymorphic Transformation in Sodium Chlorate Solution Growth

Hiromasa Niinomi, Hitoshi Miura, Yuki Kimura, Makio Uwaha, Hiroyasu Katsuno, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto

CRYSTAL GROWTH & DESIGN Vol. 14 ( 7 ) page： 3596 - 3602 2014.7

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

Chiral symmetry breaking during the chiral crystallization from a sodium chlorate (NaClO3) aqueous solution is an intriguing phenomenon because it provides insights into the prebiotic process of biohomochirality. However, a mechanism of the emergence and amplification of chirality remains controversial, especially for crystallization from highly supersaturated solution, and one of the hypotheses proposed before is a transition toward the homochiral state during the early stages of crystallization. In this contribution, we directly examined the early stage of crystallization by in situ polarized-light microscopy. The observation revealed that achiral crystals, which appear prior to the formation of chiral crystals, transform to the chiral crystal through two kinds of polymorphic transformations: (1) martensitic transformation (MT) and (2) solution-mediated phase transition (SMPT). The SMPT is remarkably facilitated by contact with a chiral crystal. Notably, the resulting enantiomorph through contact-facilitated SMPT is strongly directed by the contacting enantiomorph. In contrast, the MT yields two enantiomorphs in equal probability. The emergence and amplification of chirality has generally been considered to be a result of direct nucleation of a chiral crystal and its fragmentation. In contrast, our observations provide a possibility that the MT and contact-facilitated SMPT play a role for the emergence and amplification of chirality, respectively.

DOI： 10.1021/cg500527t

Web of Science

Scopus

Low-dislocation-density 4H-SiC crystal growth utilizing dislocation conversion during solution method Reviewed

Yuji Yamamoto, Shunta Harada, Kazuaki Seki, Atsushi Horio, Takato Mitsuhashi, Daiki Koike, Miho Tagawa, Toru Ujihara

APPLIED PHYSICS EXPRESS Vol. 7 ( 6 ) page： 065501 2014.6

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

We report a marked reduction in the dislocation density of a 4H-SiC crystal using a high-efficiency dislocation conversion phenomenon. During the solution growth, threading dislocations were efficiently converted to basal plane defects by the step flow of macrosteps. Utilizing this dislocation conversion phenomenon, we achieved the marked reduction of threading dislocation density. Consequently, the threading screw dislocation density was only 30 cm(-2), which was two orders of magnitude lower than that of the seed crystal. The 4H-SiC polytype of the seed crystal was replicated in the grown crystal, which was attributed to the spiral growth owing to a few remaining threading screw dislocations upstream of the step flow. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/APEX.7.065501

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Scopus

Solubility measurement of a metastable achiral crystal of sodium chlorate in solution growth

Hiromasa Niinomi, Atsushi Horio, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Katsuo Tsukamoto

JOURNAL OF CRYSTAL GROWTH Vol. 394 page： 106 - 111 2014.5

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

The solubility of the metastable achiral monoclinic phase in NaClO3 crystallization from an aqueous solution, which appears prior to the nucleation of chiral crystals, was successfully measured in the range from 10 degrees C to 23 degrees C. Antisolvent crystallization method was used to obtain metastable crystals for the measurement. The solubility was determined to be about 1.6 times higher than that of the chiral stable cubic phase by observing growth or dissolution of the crystal in aqueous solution at the temperature and concentration of which is predetermined. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2014.02.034

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Scopus

Nitrogen doping of 4H-SiC by the top-seeded solution growth technique using Si-Ti solvent

Kazuhiko Kusunoki, Kazuhito Kamei, Kazuaki Seki, Shunta Harada, Toru Ujihara

Journal of Crystal Growth Vol. 392 page： 60 - 65 2014.4

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

The nitrogen doping behavior of 4H-SiC was investigated by the top-seeded solution growth technique using Si-Ti solvent. Growth experiments were performed under a mixed gas of helium and nitrogen at atmospheric pressure at 1940°C, in which nitrogen content ranged between 0.17 and 0.5 vol%. The electrical property and structural quality of nitrogen-doped crystals were examined. The nitrogen doping level increased with the increase of nitrogen content in the growth furnace. The most heavily nitrogen-doped SiC with a concentration of 1.1×1020 cm-3 was obtained
however, stacking faults (SFs) were abruptly generated above a nitrogen concentration of 3.0×1019 cm-3. The lowest resistivity of approximately 0.010 Ω cm was obtained with SFs-free. Based on the both undoped and nitrogen-doped growth experimental results, the nitrogen incorporation behavior by employing our solution growth technique was discussed. © 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2014.01.044

Web of Science

Scopus

Surface Morphology and Threading Dislocation Conversion Behavior during Solution Growth of 4H-SiC Using Al-Si Solvent Reviewed

S. Harada, Y. Yamamoto, S. Xiao, M. Tagawa, and T. Ujihara

Materials Science Forum Vol. 778-780 page： 67-70 2014.1

Increase in the Growth Rate by Rotating the Seed Crystal at High Speed during the Solution Growth of SiC Reviewed

T. Umezaki, D. Koike, A. Horio, S. Harada, and T. Ujihara

Materials Science Forum Vol. 778-780 page： 63-66 2014.1

"Direct measurement of conduction miniband structure in superlattice by visible-light photoemission spectroscopy"

F. Ichihashi, D. Shimura, K. Nishitani, T. Kawaguchi, M. Kuwahara, T. Ito, S. Harada, H. Katsuno, M. Tagawa, T.Ujihara

Photovoltaic Specialist Conference (PVSC), 2014 IEEE 40th , 8-13 June 2014 page： 2882-2885 2014

Different behavior of threading edge dislocation conversion during the solution growth of 4H-SiC depending on the Burgers vector Reviewed

S. Harada, Y. Yamamoto, K. Seki, A. Horio, M. Tagawa, T. Ujihara

Acta Materialia Vol. 81 page： pp. 284-290 2014

Direct Measurement of Conduction Miniband Structure in Superlattice by Visible-Light Photoemission Spectroscopy

Ichihashi Fumiaki, Shimura Daiki, Nishitani Kenji, Kawaguchi Takahiko, Kuwahara Makoto, Ito Takahiro, Harada Shunta, Katsuno Hiroyasu, Tagawa Miho, Ujihara Tofu

2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) page： 2882 - 2885 2014

Direct Measurement of Conduction Miniband Structure in Superlattice by Visible-Light Photoemission Spectroscopy

Fumiaki Ichihashi, Daiki Shimura, Kenji Nishitani, Takahiko Kawaguchi, Makoto Kuwahara, Takahiro Ito, Shunta Harada, Hiroyasu Katsuno, Miho Tagawa, Tofu Ujihara

2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) page： 2882 - 2885 2014

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

We have proposed a novel angle-resolved photoemission spectroscopy to measure the conduction electrons emitted from a surface with negative electron affinity state. We call this method visible-light photoemission spectroscopy (VPS). In the present study, the conduction miniband structure formed in a superlattice was evaluated by the VPS method. As a result, we succeeded to obtain the dispersion of the miniband. In addition, the effective mass of the miniband was quantitatively determined from the observed dispersion. Therefore, we believe that VPS is a quite powerful tool for the evaluation of intermediate-band solar cells.

DOI： 10.1109/PVSC.2014.6925534

Web of Science

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Papers - HARADA Shunta