Faculty Profiles - HARADA Shunta

Papers - HARADA Shunta

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

T.Isogai, E. Akada, S. Nakada, N. YOshida, R. Tero,S. Harada, T. Ujihara, M. Tagawa

Japanese Journal of Applied Physics Vol. 55 page： 03DF11 2016

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

"T. Umezaki, D. Koike, S. Harada, T. Ujihara"

Japanese Journal of Applied Physics Vol. 55 ( 12 ) page： 125601 2016

Two-step SiC solution growth for dislocation reduction

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

J. Cryst. Growth 2016

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"

J. Cryst. Growth 2016

Enantioselective amplification on circularly polarized laser-induced chiral nucleation from a NaClO3 solution containing Ag nanoparticles

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

CrystEngComm Vol. 18 page： 7441-7448 2016

Enantioselective amplification on circularly polarized laser-induced chiral nucleation from a NaClO3 solution containing Ag nanoparticles

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

CRYSTENGCOMM Vol. 18 ( 39 ) page： 7441 - 7448 2016

Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

We demonstrate that a statistically-significant chiral bias in NaClO3 chiral crystallization can be provoked by inducing nucleation via the optical trapping of Ag nano-aggregates using a continuous wave visible circularly polarized laser (lambda = 532 nm). The laser was focused at the interface between air and an unsaturated NaClO3 aqueous solution containing Ag nanoparticles. The "dominant" enantiomorph was switchable by changing the handedness of the incident circularly polarized laser, indicating that the chiral bias is enantio-selective. Moreover, it has been found that the resulting crystal enantiomeric excess (CEE) reached approximately 25%. The CEE is much higher than the typical enantiomeric excess (EE) in the asymmetric photosynthesis of organic compounds ranging from 0.5 to 2%. The efficient induction of the nucleation and the large chiral bias imply the contribution of localized surface plasmon resonance of the Ag nanoaggregates to chiral nucleation. Our method has potential to offer the benefit for studies on the spatiotemporal nucleation control, optical resolution of chiral compounds and biohomochirality.

DOI： 10.1039/c6ce01464j

Web of Science

Scopus

High-speed solution growth of single crystal AlN from Cr-Co-Al solvent Reviewed

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

Materials Science Forum Vol. 858 page： 1210 - 1213 2016

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

We achieved high-speed solution growth of AlN single crystal from Cr-Co-Al solvent, which was designed on the basis of thermodynamic calculation. To avoid the unintentional precipitations at the interface between solution and gas as well as to increase the growth rate, we designed the solution growth condition, in which the solution near the interface is undersaturated and the solution near the growth position is supersaturated. To realize this kind of ideal condition, we selected Co and Cr as solvent materials due to their high affinity with nitrogen or aluminum. Finally, we achieved a growth rate as high as 200 μm/h in maximum.

DOI： 10.4028/www.scientific.net/MSF.858.1210

Scopus

Spatial distribution of carrier concentration in 4H-SiC crystal grown by solution method Reviewed

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

Materials Science Forum Vol. 858 page： 57 - 60 2016

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

We investigated the spatial distribution of carrier concentration in n-type 4H-SiC grown by the solution method using the peak frequency of the longitudinal optical phonon-plasmon coupled (LOPC) mode of the Raman spectra on the surface. The carrier concentration at the position of the smooth terrace was higher than the carrier concentration at the position where the macrosteps were formed. This indicates the nitrogen incorporation efficiently occurs on the smooth surface where the density of macrosteps is relatively low. The different incorporation of nitrogen depending on the surface morphology can be understood from the view point of the adsorption time of impurity on the terrace. The present result implies that the uniform surface morphology is necessary to achieve uniform doping concentration in SiC crystal.

DOI： 10.4028/www.scientific.net/MSF.858.57

Scopus

Proposal of visible-light photoemmision spectroscopy for the evaluation of conduction band in semiconductors

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

Abstract of annual meeting of the Surface Science of Japan Vol. 36 ( 0 ) page： 338 - 338 2016

Measurement of energy distribution of conduction electrons in superlattice by visible-light photoemission spectroscopy

Ichihashi F.

2015 IEEE 42nd Photovoltaic Specialist Conference, PVSC 2015 2015.12

Non-uniform electrodeposition of zinc on the (0001) plane

Mitsuhashi Takato, Ito Yasumasa, Takeuchi Yukihisa, Harada Shunta, Ujihara Toru

THIN SOLID FILMS Vol. 590 page： 207 - 213 2015.9

Effect of aluminum addition on the surface step morphology of 4H-SiC grown from Si-Cr-C solution

Takeshi Mitani, Naoyoshi Komatsu, Tetsuo Takahashi, Tomohisa Kato, Shunta Harada, Toru Ujihara, Yuji Matsumoto, Kazuhisa Kurashige, Hajime Okumura

JOURNAL OF CRYSTAL GROWTH Vol. 423 page： 45 - 49 2015.8

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

For the solution growth of 4H-SiC with Si1-xCrx solvents, the change in surface step structure by 4 at% Al addition to the solvent was investigated. Without Al addition, step bunching resulted in the formation of giant macrosteps with height greater than several micrometers, and trench-like surface defects formed with solvent inclusion. The edge of the giant macrosteps composing trench-like defects was faceted into low-index facet planes, (1 (1) over bar 0m) (m=1-4). The formation of the trench-like surface defects is considered to originate from the self-pinning of macrosteps owing to the step-faceting phenomenon, which facilitates further development of macrosteps. On the other hand, the addition of Al to the solvents significantly improved the surface roughening, and suppressed the formation of the trench-like surface defects. In this case, smaller bunched steps with heights from several nanometers to about 10 nm formed on the terraces of the macrosteps, while regularly arranged trains of unit-cell-size steps formed on the terrace of macrosteps in growth without Al addition. The decrease in step stiffness might be a possible cause for the formation of the smaller bunched steps on the terrace in growth with Al addition. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2015.04.032

Web of Science

Scopus

"Effect of aluminum addition on the surface step morphology of 4H-SiC grown from Si-Cr-C solution" Reviewed

Takeshi Mitani, Naoyoshi Komatsu, Tetsuo Takahashi, Tomohisa Kato, Shunta Harada, Toru Ujihara, Yuji Matsumoto, Kazuhisa Kurashige, Hajime Okumura

Journal of Crystal Growth Vol. 423 page： 45–49 2015.8

Non-uniform electrodeposition of zinc on the (0001) plane Reviewed

T. Mitsuhashi, Y. Ito, Y. Takeuchi, S. Harada,T. Ujihara

Thin Solid Films Vol. 590 page： 207-213 2015.6

Non-uniform electrodeposition of zinc on the (0001) plane Reviewed

T. Mitsuhashi, Y. Ito, Y. Takeuchi, S. Harada, T. Ujihara

Thin Solid Films Vol. 590 page： 207-213 2015.6

3C-SiC crystal on sapphire by solution growth method Reviewed

Kenji Shibata, Shunta Harada, Toru Ujihara

Materials Science Forum Vol. 821-823 page： 185 - 188 2015

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

We realized the growth of 3C-SiC crystal on sapphire by solution growth method. The carbon deposition on a sapphire substrate before growth is the key point for this technology. This carbon layer plays a role to protect the dissolution of sapphire by Si solvent. 3C-SiC was grown on the whole surface of the sapphire substrate and some of the film was 3C-SiC single crystal. Surprisingly, the 3C-SiC layer did not directly grown on the sapphire substrate. The single crystal 3C-SiC layer formed by the reaction between the deposited carbon and the Si wafer that is a solvent material below the melting point of silicon during heating process before the growth. The 3C-SiC grew on Sapphire substrate. In this process, the deposited carbon play another important role.

DOI： 10.4028/www.scientific.net/MSF.821-823.185

Scopus

Dislocation conversion during sic solution growth for high-quality crystals Reviewed

Shunta Harada, Yuji Yamamoto, Shi Yu Xiao, Daiki Koike, Takuya Mutoh, Kenta Murayama, Kenta Aoyagi, Takenobu Sakai, Miho Tagawa, Toru Ujihara

Materials Science Forum Vol. 821-823 page： 3 - 8 2015

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

Solution growth of SiC has attracted significant attention due to its potential for the production of high-quality SiC wafers. We have recently investigated the dislocation propagation behavior during SiC solution growth with the aim of reducing the dislocation density. Threading dislocations were found to be converted to defects on the basal planes during solution growth. Utilizing this dislocation conversion phenomenon, we have proposed a dislocation reduction process during solution growth and achieved high-quality 4H-SiC crystal growth. Here we confirm the potential of SiC solution growth for the production of high-quality SiC wafers.

DOI： 10.4028/www.scientific.net/MSF.821-823.3

Scopus

Control of interface shape by non-axisymmetric solution convection in top-seeded solution growth of SiC crystal Reviewed

Daiki Koike, Tomonori Umezaki, Kenta Murayama, Kenta Aoyagi, Shunta Harada, Miho Tagawa, Takenobu Sakai, Toru Ujihara

Materials Science Forum Vol. 821-823 page： 18 - 21 2015

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

We achieved the convex growth interface shape in top-seeded solution growth of SiC applying non-axisymmetric solution convection induced by non-axisymmetric temperature distribution. The detailed solution flow, temperature distribution and carbon concentration distribution were calculated by 3-dimensional numerical analysis. In the present case, the solution flow below the crystal was unidirectional and the supersaturation was increased along the solution flow direction. By the rotation of the crystal in the unidirectional flow and the temperature distribution, we successfully obtained the crystal with the convex growth interface shape.

DOI： 10.4028/www.scientific.net/MSF.821-823.18

Scopus

Improvement of surface morphology by solution flow control in solution growth of SiC on off-axis seeds Reviewed

Tomonori Umezaki, Daiki Koike, Shunta Harada, Toru Ujihara

Materials Science Forum Vol. 821-823 page： 31 - 34 2015

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

The solution growth of SiC on an off-axis seed is effective on the reduction of threading dislocations. We proposed a novel method to grow a SiC crystal on an off-axis seed by top-seeded solution growth (TSSG). In our previous study, a unidirectional solution flow above a seed crystal is effective to suppress surface roughness in the growth on the off-axis seed. However, it is difficult to apply the unidirectional flow in an axisymmetric TSSG set-up. In this study, the unidirectional flow could be achieved by shifting the rotational axis away from the center of the seed crystal. As a result, the smooth surface was obtained in the wider area where the solution flow direction was opposite to the step-flow direction.

DOI： 10.4028/www.scientific.net/MSF.821-823.31

Scopus

Research on solvent composition for different surface morphology on C face during 4H-SiC solution growth Reviewed

Shi Yu Xiao, Natsumi Hara, Shunta Harada, Kenta Murayama, Kenta Aoyagi, Takenobu Sakai, Toru Ujihara

Materials Science Forum Vol. 821-823 page： 39 - 42 2015

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

Surface morphology of the SiC crystal grown on the C face of the 4H-SiC seed crystal by TSSG method using pure Si, Si-1at%Ti-C, Si-5at%Ti-C and Si-20at%Ti-C solvents was investigated. The surface morphology of the crystal grown from pure Si solvent was smooth. By the addition of Ti to the solvent, the surface morphology became rougher. The RMS value is not proportional to the concentration of Ti. The formation of macrosteps with several micrometers was observed when the addition of Ti increased to 5at% indicating the possibility of the threading screw dislocation conversion on the C face of the 4H-SiC crystal.

DOI： 10.4028/www.scientific.net/MSF.821-823.39

Scopus

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Papers - HARADA Shunta