Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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Formation of basal plane dislocations introduced by collision of macrosteps on growth surface during sic solution growth

T. Hori, K. Murayama, S. Harada, S. Xiao, M. Tagawa, T. Ujihara

Materials Science Forum Vol. 897 page： 28 - 31 2017

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

The relationship between surface morphology and spatial distribution of basal plane dislocations in 4H-SiC crystal grown by top-seeded solution growth on the C face was investigated by the differential interference microscopy as well as X-ray topography. Basal plane dislocations were generated at the boundaries of the domains with the different macrosteps advance directions. On the other hand, at the area where macrosteps advance to the same directions, BPDs were hardly observed. This results suggest that BPD density can be decreased by the suppression of the collision of macrosteps during the solution growth on the C face controlling the surface morphology.

DOI： 10.4028/www.scientific.net/MSF.897.28

Scopus

Sic solution growth on si face with extremely low density of threading screw dislocations for suppression of polytype transformation

K. Murayama, T. Hori, S. Harada, S. Xiao, M. Tagawa, T. Ujihara

Materials Science Forum Vol. 897 page： 24 - 27 2017

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

In order to achieve a high-quality SiC crystal in solution growth, one of the most difficult issues is to grow a thick layer on Si face avoiding polytype transformation. In this case, two-dimensional nucleation, which leads to the polytype transformation, is frequently induced because a density of threading screw dislocations acting as a source of spiral step decreases and wide terraces form by step bunching as growth proceeds. Therefore, it is very difficult to stabilize the polytype of crystals grown with extremely low density of threading screw dislocations. In this study, we tried to overcome these problems by using specially designed seed crystal and optimizing growth temperature and temperature distribution. We successfully grew thick low-threading-dislocation density SiC crystal without polytype transformation under the condition of high growth temperature and homogeneous temperature distribution.

DOI： 10.4028/www.scientific.net/MSF.897.24

Scopus

Solvent design for high-purity SiC solution growth

Shunta Harada, Goki Hatasa, Kenta Murayama, Tomohisa Kato, Miho Tagawa, Toru Ujihara

Materials Science Forum Vol. 897 page： 32 - 35 2017

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

In order to design a solvent for high-purity SiC solution growth, the impurity incorporation and the carbon solubility of various solvent materials have been investigated. Among the transition metal elements, the impurity elements of Cr, Ti, V and Hf are more readily incorporate during the solution growth than the other transition metal elements. The thermodynamic calculation revealed that the Y-Si solvent has relatively large carbon solubility, which is comparable to the Cr-Si and Ti-Si solvents often used in the solution growth of bulk SiC crystals. From these results, the Y-Si solvent is expected to be a suitable solvent for the high-purity SiC solution growth. Furthermore, we have demonstrated that the Y-Si solvent can achieve lower incorporation of metal impurity in the grown crystal than the Cr-Si solvent maintaining the growth rate.

DOI： 10.4028/www.scientific.net/MSF.897.32

Scopus

Plasmonic Heating-Assisted Laser-Induced Crystallization from a NaClO3 Unsaturated Mother Solution

"H. Niinomi, T. Sugiyama, M. Tagawa, M. Maruyama, T. Ujihara, T. Omatsu, Y. Mori"

Cryst. Growth Des. 2016.12

Plasmonic Heating-Assisted Laser-Induced Crystallization from a NaClO3 Unsaturated Mother Solution

H. Niinomi, T. Sugiyama, M. Tagawa, M. Maruyama, T. Ujihara, T. Omatsu, Y. Mori

Cryst. Growth Des. 2016.12

Analysis of the carbon transport near the growth interface with respect to the rotational speed of the seed crystal during top-seeded solution growth of SiC

Tomonori Umezaki, Daiki Koike, Shunta Harada, Toru Ujihara

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 55 ( 12 ) page： 125601 2016.12

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

One of the most important issues of SiC solution growth is to increase the growth rate. In our previous study, we reported that increasing the rotational speed of the seed crystal is effective for improving the growth rate in top-seeded solution growth. In the present study, we investigated the origin of the growth rate improvement through a continuous fluid dynamics simulation with a full-scale three-dimensional model of the experimental setup for actual growth experiment. The numerical results indicated that the stagnant layer above the growth interface decreased in thickness and the carbon concentration gradient then became steep with an increase in the rotational speed of the seed crystal. The experimental growth rate was proportional to the calculated carbon concentration gradient, which indicates that the carbon diffusion through the stagnant layer is the rate-determining process. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.125601

Web of Science

Scopus

Conversion Behavior of Threading Screw Dislocations on C Face with Different Surface Morphology During 4H-SiC Solution Growth

Xiao Shiyu, Harada Shunta, Murayama Kenta, Tagawa Miho, Ujihara Toru

CRYSTAL GROWTH & DESIGN Vol. 16 ( 11 ) page： 6436 - 6439 2016.11

Conversion behavior of threading screw dislocations on C face with different surface morphology during 4H-SiC solution growth

"S. Xiao, S. Harada, K. Murayama, M. Tagawa, T. Ujihara"

Cryst. Growth Des. page： 6436–6439 2016.10

Conversion behavior of threading screw dislocations on C face with different surface morphology during 4H-SiC solution growth

S. Xiao, S. Harada, K. Murayama, M. Tagawa, T. Ujihara

Cryst. Growth Des. page： 6436–6439 2016.10

Characterization of V-Shaped Defects Formed during the 4H-SiC Solution Growth by Transmission Electron Microscopy and X-ray Topography Analysis

Xiao Shiyu, Harada Shunta, Murayama Kenta, Ujihara Toni

CRYSTAL GROWTH & DESIGN Vol. 16 ( 9 ) page： 5136 - 5140 2016.9

Characterization of V-shaped defects formed during the 4H-SiC solution growth by transmission electron microscopy and X-ray topography analysis

"S. Xiao, S. Harada, K. Murayama, T. Ujihara"

Cryst. Growth Des. Vol. 16 ( 9 ) page： 5136-5140 2016.7

Enantioselective amplification on circularly polarized laser-induced chiral nucleation from a NaClO 3 solution containing Ag nanoparticles

"H. Niinomi, T. Sugiyama, M. Tagawa, K. Murayama, S. Harada, T. Ujihara"

CrystEngComm Vol. 18 ( 39 ) page： 7441-7448 2016.7

Characterization of V-shaped defects formed during the 4H-SiC solution growth by transmission electron microscopy and X-ray topography analysis

S. Xiao, S. Harada, K. Murayama, T. Ujihara

Cryst. Growth Des. Vol. 16 ( 9 ) page： 5136-5140 2016.7

Enantioselective amplification on circularly polarized laser-induced chiral nucleation from a NaClO 3 solution containing Ag nanoparticles

H. Niinomi, T. Sugiyama, M. Tagawa, K. Murayama, S. Harada, T. Ujihara

CrystEngComm Vol. 18 ( 39 ) page： 7441-7448 2016.7

Spatial Distribution of Carrier Concentration in 4H-SiC Crystal Grown by Solution Method Reviewed

Zhen Jiang Wang, Takahiko Kawaguchi, Kenta Murayama, Kenta Aoyagi, S. Harada, Miho Tagawa, Takenobu Sakai, Tomohisa Kato, Toru Ujihara

Materials Science Forum Vol. 858 page： 57-60 2016.5

High-Speed Solution Growth of Single Crystal AlN from Cr-Co-Al Solvent Reviewed

Shota Watanabe, Masashi Nagaya, Yukihisa Takeuchi, Kenta Aoyagi, S. Harada, Miho Tagawa, Toru Ujihara

Materials Science Forum Vol. 858 page： 1210-1213 2016.5

Effect of magnesium ion concentration on two-dimensional structure of DNA-functionalized nanoparticles on supported lipid bilayer Reviewed

Takumi Isogai, Eri Akada, Sakiko Nakada, Naoya Yoshida, Ryugo Tero, Shunta Harada, Toru Ujihara, Miho Tagawa

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 55 ( 3 ) page： 03DF11 2016.3

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

The effect of divalent cations on lipid-bilayer-assisted DNA-functionalized nanoparticle (DNA-NP) assembly has been studied. We previously reported the lateral diffusion of DNA-NPs on planar lipid bilayer patches, owing to the mobility of lipid molecules in a supported lipid bilayer (SLB), and the resultant two-dimensional (2D) assembly of DNA-NPs. We here report the structural change of the assembled 2D DNA-NP lattices by magnesium ion concentration control on a successfully formed uniform SLB. In the magnesium-free buffer solution, DNA-NPs on SLB loosely assembled into quasi-hexagonal ordered lattices. In buffer solution containing 1mM magnesium acetate, the interparticle distance of DNA-NPs decreased and the lattice structure became disordered. In buffer solution containing 5mM magnesium acetate, the structure of DNA-NP arrays changed markedly and square lattices appeared. It is suggested that magnesium ions affected DNA molecules, which linked nanoparticles, and enabled the control of the structure of DNA-NP 2D arrays. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.03DF11

Web of Science

Scopus

Polytype control by activity ratio of silicon to carbon during SiC solution growth using multicomponent solvents Reviewed

Atsushi Horio, Shunta Harada, Daiki Koike, Kenta Murayama, Kenta Aoyagi, Takenobu Sakai, Miho Tagawa, Toru Ujihara

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 55 ( 1 ) page： 01AC01 2016.1

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

We report on the relationship between grown polytypes and the activity ratio of silicon to carbon during SiC solution growth using multicomponent solvents. From the thermodynamic calculation as well as crystallization experiments, we revealed that a high activity ratio (a(Si)/a(C)) in the solution leads to the growth of low-hexagonality polytypes, and low a(Si)/a(C) results in the growth of high-hexagonality polytypes. 4H-SiC is stable when a(Si)/a(C) is relatively low (similar to 10(1) > a(Si)/a(C)), 3C-SiC is stable when a(Si)/a(C) is relatively high (similar to 10(4) < a(Si)/a(C)), and 6H-SiC is stable in the intermediate a(Si)/a(C) range (similar to 10(2) < a(Si)/a(C) < similar to 10(3)). From these results, the Cr-Si solvent at high temperatures is expected to be suitable for 4H-SiC growth, and Sc-Si and Fe-Si solvents at relatively low temperatures are expected to be suitable for 3C-SiC growth. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.01AC01

Web of Science

Scopus

Thin film growth of CaFe2As2 by molecular beam epitaxy Reviewed

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

SUPERCONDUCTOR SCIENCE & TECHNOLOGY Vol. 29 ( 1 ) page： 015013 2016.1

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

Film growth of CaFe2As2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe2As2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45 degrees-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45 degrees-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch.

DOI： 10.1088/0953-2048/29/1/015013

Web of Science

Scopus

Polytype control by activity ratio of silicon to carbon during SiC solution growth using multicomponent solvents Reviewed

A. Horio, S. Harada, D. Koike, K. Murayama, K. Aoyagi, T. Sakai, M. Tagawa, T. Ujihara

Japanese Journal of Applied Physics Vol. 55 page： 01AC01 2016

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Papers - HARADA Shunta