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Journal Articles

Out-of-plane strain induced in a Moir$'e$ superstructure of monolayer MoS$$_{2}$$ and MoSe$$_{2}$$ on Au(111)

Yasuda, Satoshi; Takahashi, Ryosuke*; Osaka, Ryo*; Kumagai, Ryota*; Miyata, Yasumitsu*; Okada, Susumu*; Hayamizu, Yuhei*; Murakoshi, kei*

Small, 13(31), p.1700748_1 - 1700748_8, 2017/08

 Times Cited Count:9 Percentile:53.89(Chemistry, Multidisciplinary)

MoS$$_{2}$$ and MoSe$$_{2}$$ monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out-of-plane strain in both MoS$$_{2}$$ and MoSe$$_{2}$$ layers, whereas no strain generation is observed on polycrystalline Au or SiO$$_{2}$$/Si surfaces. Scanning tunneling microscopy analysis provides information regarding consequent specific adsorption sites between lower S (Se) atoms in the S-Mo-S (Se-Mo-Se) structure and Au atoms via unique moir$'e$ superstructure formation for MoS$$_{2}$$ and MoSe$$_{2}$$ layers on Au(111). This observation indicates that the specific adsorption sites give rise to out-of-plane strain in the TMDC layers. Furthermore, it also leads to effective modulation of the electronic structure of the MoS$$_{2}$$ or MoSe$$_{2}$$ layer.

Journal Articles

Fabrication of Pt nanoparticle incorporated polymer nanowires by high energy ion and electron beam irradiation

Tsukuda, Satoshi*; Takahashi, Ryota*; Seki, Shuhei*; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Tanaka, Shunichiro*

Radiation Physics and Chemistry, 118, p.16 - 20, 2016/01

 Times Cited Count:1 Percentile:14.27(Chemistry, Physical)

Polyvinylpyrrolidone (PVP)-Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including H$$_{2}$$PtCl$$_{6}$$. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and H$$_{2}$$PtCl$$_{6}$$. However, increasing the amount of H$$_{2}$$PtCl$$_{6}$$ led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.

Journal Articles

Controls over structural and electronic properties of epitaxial graphene on silicon using surface termination of 3C-SiC(111)/Si

Fukidome, Hirokazu*; Abe, Shunsuke*; Takahashi, Ryota*; Imaizumi, Kei*; Inomata, Shuya*; Handa, Hiroyuki*; Saito, Eiji*; Enta, Yoshiharu*; Yoshigoe, Akitaka; Teraoka, Yuden; et al.

Applied Physics Express, 4(11), p.115104_1 - 115104_3, 2011/11

 Times Cited Count:34 Percentile:80.78(Physics, Applied)

Journal Articles

Control of epitaxy of graphene by crystallographic orientation of a Si substrate toward device applications

Fukidome, Hirokazu*; Takahashi, Ryota*; Abe, Shunsuke*; Imaizumi, Kei*; Handa, Hiroyuki*; Kang, H. C.*; Karasawa, Hiromi*; Suemitsu, Tetsuya*; Otsuji, Taiichi*; Enta, Yoshiharu*; et al.

Journal of Materials Chemistry, 21(43), p.17242 - 17248, 2011/11

 Times Cited Count:28 Percentile:67.71(Chemistry, Physical)

Journal Articles

Low-energy-electron-diffraction and X-ray-phototelectron-spectroscopy studies of graphitization of 3C-SiC(111) thin film on Si(111) substrate

Takahashi, Ryota*; Handa, Hiroyuki*; Abe, Shunsuke*; Imaizumi, Kei*; Fukidome, Hirokazu*; Yoshigoe, Akitaka; Teraoka, Yuden; Suemitsu, Maki*

Japanese Journal of Applied Physics, 50(7), p.070103_1 - 070103_6, 2011/07

 Times Cited Count:31 Percentile:78.66(Physics, Applied)

Journal Articles

Oxygen-induced reduction of the graphitization temperature of SiC surface

Imaizumi, Kei*; Handa, Hiroyuki*; Takahashi, Ryota*; Saito, Eiji*; Fukidome, Hirokazu*; Enta, Yoshiharu*; Teraoka, Yuden; Yoshigoe, Akitaka; Suemitsu, Maki*

Japanese Journal of Applied Physics, 50(7), p.070105_1 - 070105_6, 2011/07

 Times Cited Count:4 Percentile:20.9(Physics, Applied)

Journal Articles

X-ray and neutron protein crystallographic analysis of the trypsin-BPTI complex

Kawamura, Kenji*; Yamada, Taro*; Kurihara, Kazuo; Tamada, Taro; Kuroki, Ryota; Tanaka, Ichiro*; Takahashi, Haruyuki*; Niimura, Nobuo*

Acta Crystallographica Section D, 67(2), p.140 - 148, 2011/02

 Times Cited Count:23 Percentile:87.3(Biochemical Research Methods)

Journal Articles

Growth of large protein crystals by a large-scale hanging-drop method

Kakinouchi, Keisuke*; Nakamura, Tsutomu*; Tamada, Taro; Adachi, Hiroaki*; Sugiyama, Shigeru*; Maruyama, Mihoko*; Takahashi, Yoshinori*; Takano, Kazufumi*; Murakami, Satoshi*; Inoue, Tsuyoshi*; et al.

Journal of Applied Crystallography, 43(4), p.937 - 939, 2010/08

 Times Cited Count:4 Percentile:50.4(Chemistry, Multidisciplinary)

A method for growing large protein crystals is described. In this method, a cut pipette tip is used to hang large-scale droplets (maximum volume 200 $$mu$$l) consisting of protein and precipitating agents. A crystal grows at the vapor-liquid interface; thereafter the grown crystal can be retrieved by droplet-droplet contact both for repeated macroseeding and for mounting crystals in a capillary. Crystallization experiments with peroxiredoxin of ${it Aeropyrum pernix}$ K1(thioredoxin peroxidase, ApTPx) and hen egg white lysozyme demonstrated that this large-scale hanging-drop method could produce a large-volume crystal very effectively. A neutron diffraction experiment confirmed that an ApTPx crystal (6.2 mm$$^{3}$$) obtained by this method diffracted to beyond 3.5 ${AA}$ resolution.

Journal Articles

Crystal growth procedure of HIV-1 protease-inhibitor KNI-272 complex for neutron structural analysis at 1.9 ${AA}$ resolution

Shimizu, Noriko*; Sugiyama, Shigeru*; Maruyama, Mihoko*; Takahashi, Yoshinori*; Adachi, Motoyasu; Tamada, Taro; Hidaka, Koshi*; Hayashi, Yoshio*; Kimura, Toru*; Kiso, Yoshiaki*; et al.

Crystal Growth & Design, 10(7), p.2990 - 2994, 2010/06

 Times Cited Count:11 Percentile:73.7(Chemistry, Multidisciplinary)

We report crystal growth of human immunodeficiency virus 1 protease (HIV PR) in a complex with its inhibitor KNI-272 by six different methods. Comparative analysis indicates that top-seeded solution growth (TSSG) and TSSG combined with the floating and stirring technique (TSSG-FAST) are efficient strategies for rapidly obtaining large single crystals and effectively preventing polycrystallization of the seed crystal. Neutron diffraction analysis confirmed that the crystalobtained by TSSG is a high-quality single crystal. Furthermore, crystal shape was observed to be influenced by solution flow, suggesting that the degree of supersaturation significantly affects the crystal growth direction of HIV PR complex. This finding implies that the shape of the HIV PR complex crystal might be controlled by the solution flow rate.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Oral presentation

Epitaxy of graphene on Si substrates toward three-dimensional graphene devices

Fukidome, Hirokazu*; Miyamoto, Yu*; Handa, Hiroyuki*; Takahashi, Ryota*; Imaizumi, Kei*; Suemitsu, Maki*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

Graphene, two-dimensional network of sp$$^{2}$$ carbon, is one of promising materials beyond CMOS, as described in the semiconductor roadmap. The major issue is a lack of reasonable process for epitaxial growth on substrates. In fact, current production methods, such as exfoliation from graphite and epitaxy on SiC single crystals, are not mass-productive. We are seeking the ways to develop graphene-on-silicon (3D-GOS) process to match recent trends of silicon technologies. One of key issues toward 3D-GOS is the formation of epitaxial graphene on main plane directions of silicon, such as (100), (110) and (111). In this article, large area epitaxy of graphene on Si(110), Si(100) and Si(111) is presented. The result must be a good news because it can open new and realistic ways to three-dimensionally fabricate graphene-based devices beyond CMOS.

Oral presentation

LEED observation for surface structure of graphene on silicon

Takahashi, Ryota*; Miyamoto, Yu*; Handa, Hiroyuki*; Saito, Eiji*; Imaizumi, Kei*; Fukidome, Hirokazu*; Suemitsu, Maki*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

We have succeeded to form graphene films from 3C-SiC layer on Si substrate by thermal annealing in vacuum (graphene on silicon technique:GOS). In this study, surface structures were observed by LEED and XPS methods to make clear the GOS formation mechanisms. SiC-1$$times$$1 LEED pattern was observed at 3C-SiC(111) surface on the Si substrate showing periodicity of bulk SiC. After graphene formation treatments of 1523 K thermal annealing for 30 min, graphene 1$$times$$1 pattern was observed showing periodicity of graphene. The graphene (1$$times$$1) spots were tilted by 30 deg comparing to the bulk SiC (1$$times$$1) spots. C1s-XPS observation revealed that a peak corresponding to sp$$^{2}$$ bonding increased with decreasing SiC bulk peak. Consequently, graphene formation from 3C-SiC on Si substrate is same as that on 6H-SiC(0001) substrate.

Oral presentation

Reduction of graphitization temperature of SiC surface by addition of oxygen

Imaizumi, Kei*; Takahashi, Ryota*; Miyamoto, Yu*; Handa, Hiroyuki*; Saito, Eiji*; Fukidome, Hirokazu*; Suemitsu, Maki*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

As the graphene, 2D-crystal of a carbon atomic layer, has a large mobility of 300000 cm$$^{2}$$/V/s, it is expected as a candidate for the next generation electronic device material. As to the practical use of graphene, a graphene-on-silicon (GOS) technique in which graphene is formed by thermal annealling on an silicon substrate covered by an SiC thin film. Since the anneal temperature is high as 1523-1573 K for the graphene formation in the former techniques including the GOS technique, such a high temperature technique is not introduced indeed in silicon device fabrication processes. We noticed a temperature-pressure phase diagram reported by Yongwei Song et al.. We have succeeded to form a graphene film on the SiC surface at a lower temperature of 1273 K by adding a bit of oxygen gas in the anneal atmosphere.

Oral presentation

LEED and XPS observations of graphene-on-Si process

Takahashi, Ryota*; Miyamoto, Yu*; Handa, Hiroyuki*; Saito, Eiji*; Imaizumi, Kei*; Fukidome, Hirokazu*; Suemitsu, Maki*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

In this study, a graphene-on-silicon process was observed by LEED and XPS to make clear mechanisms. LEED patterns of SiC(1$$times$$1) and Si(RT3$$times$$RT3)R30$$^{circ}$$ were observed on the 3C-SiC(111) surface formed on the Si(111) surface. After the thermal annealing process at 1523 K for 30 min, a LEED pattern of graphene(1$$times$$1) was also observed. The graphene(1$$times$$1) pattern was tilted to the SiC(1$$times$$1) pattern by 30 deg as expected. The graphene formation process of 3C-SiC(111) on the Si(111) is the same as that of a 6H-SiC(0001) substrate. Comparing a C1s photoemission peak before and after the annealling process, a Cis peak corresponding to an sp$$^{2}$$ hybrid orbital appeared and a peak due to SiC bulk decreased. These facts reveal that a surface state transformation from SiC(1$$times$$1)(bulk state) to graphene(1$$times$$1)(graphene state) takes place even in the graphene-on-silicon process on Si(111) surface as well as the graphene formation process on the 6H-SiC(0001) substrate.

Oral presentation

SR-PES study on the formation of epitaxial graphene on Si substrates

Suemitsu, Maki*; Takahashi, Ryota*; Handa, Hiroyuki*; Saito, Eiji*; Imaizumi, Kei*; Fukidome, Hirokazu*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

The up-to-date industrial fabrication method of graphene is a epitaxial graphene method, in which graphene layers are formed on the SiC substrate after thermal annealing in the vacuum condition. This method, however, has a large disadvantage, that is, an SiC bulk substrate with a large size diameter is not available with low prices. We have succeeded to make graphene on the Si substrate by thermal annealing of a 3C-SiC ultra-thin layer (80-100 nm) formed epitaxially on the Si substrate in the vacuum conditions (Graphene-On-Silicon;GOS). In this study, in order to make clear mechanisms of the GOS formation processes, low energy electron diffraction (LEED) and X-ray photoemission spectroscopy (XPS) have been applied to observe surface structures. Consequently, graphene formation processes from the 3C-SiC(111) layer on the Si(111) substrate has been found to be same as those on the 6H-SiC(0001) substrate.

Oral presentation

Controlling the interface between graphene and SiC by use of graphene-on-silicon technology

Fukidome, Hirokazu*; Takahashi, Ryota*; Imaizumi, Kei*; Handa, Hiroyuki*; Suemitsu, Maki*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

Graphene layers could be formed firstly on an SiC thin film, which is fabricated on an Si substrate by a gas-source MBE method, by thermal annealing in vacuum (GOS structure). It should be controlled the interface between the SiC film and the graphene layers. In this study, relationships between chrystallographic symmetries of the Si substrate and the interface in the GOS structure were investigated. After an SiC(110), SiC(100), and SiC(111) surface is formed on the Si(110), Si(100), and Si(111) substrate, respectively, graphene layers were formed by thermal annealing of these SiC thin films up to 1523 K in vacuum. Photoemission spectroscopy of C1s core level with synchrotron radiation revealed that no interfacial layers are formed between the graphene and the SiC(110) and SiC(100) films while an interfacial layer is formed on the SiC(111) film.

Oral presentation

Real-time SR photoelectron-spectroscopy measurement of low-temperature graphitization of a SiC thin film on Si substrates under ULP oxygen ambient

Imaizumi, Kei*; Takahashi, Ryota*; Handa, Hiroyuki*; Saito, Eiji*; Fukidome, Hirokazu*; Suemitsu, Maki*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

We found that an SiC surface changed to a graphene film even at 1273 K in the oxygen gas ambient. As subsequent experiments, real-time photoelectron spectroscopy using synchrotron radiation was applied to observe the graphene formation process in the ultra low pressure oxygen ambient. The 3C-SiC(111) surface, formed on the Si(111) surface using monomethylsilane, was used as a substrate. The real-time photoelectron spectroscopy was performed at BL23SU in the SPring-8. With increasing reaction time, a C1s photoelectron peak originated from sp$$^{2}$$ carbon increased. It reveals that a graphene film is formed on the SiC surface.

Oral presentation

LEED observation of formation of epitaxial graphene on 3C-SiC(111) ultrathin film

Takahashi, Ryota*; Miyamoto, Yu*; Handa, Hiroyuki*; Saito, Eiji*; Imaizumi, Kei*; Fukidome, Hirokazu*; Suemitsu, Maki*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

New technologies beyond Si-CMOS technologies are neccessary in the Si electronic device developments. Now, graphene is attracted as it has a large mobility. It is well known that a 6H-SiC substrate surface changes to graphene by thermal annealing in vacuum as Si atoms sublimate. On the other hand, we developed the graphene-on-silicon (GOS) method in which graphene is formed from 3C-SiC thin film on an Si substrate by thermal annealing in vacuum. In this report, graphene formation processes were observed by LEED for a 6H-SiC(0001) substrate and a 3C-SiC(111) surface. It was found that the graphene formation process on a 3C-SiC(111) surface proceeded through the same surface reconstruction structure with that of 6H-SiC(0001) substrate.

Oral presentation

Orientation-mediated control of interfacial structure in epitaxial graphene on silicon substrates

Suemitsu, Maki*; Fukidome, Hirokazu*; Takahashi, Ryota*; Imaizumi, Kei*; Handa, Hiroyuki*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

Formation of SiC thin layers on Si substrates followed by annealing converts the top surface into graphene (graphene on silicon;GOS). Normally, 3C-SiC(111), (110) and (100)-oriented layers are grown on Si(111), (110) and (100) substrates, respectively. Not only 3C-SiC(111) but also 3C-SiC(100) and (110) surfaces, epitaxial graphene layers were produced. The Raman spectra showed the same bands for the three orientations. Synchrotron-radiation X-ray photoelectron spectrum of C1s presented sp$$^{2}$$ carbon atoms for the three orientations. While no interfacial layers are formed on the SiC(100) and SiC(110), the interfacial layer does exist between the graphene and the SiC(111) film. The observation of the equally successful growth of graphene on these low-index SiC surfaces makes the GOS technology aviable in the post-Si device developments.

Oral presentation

Viability of graphene-on-silicon technology toward fusion of graphene with advanced Si-CMOS technologies

Fukidome, Hirokazu*; Takahashi, Ryota*; Miyamoto, Yu*; Handa, Hiroyuki*; Kang, H. C.*; Karasawa, Hiromi*; Suemitsu, Tetsuya*; Otsuji, Taiichi*; Yoshigoe, Akitaka; Teraoka, Yuden; et al.

no journal, , 

By forming an SiC thin film on Si substrates and by thermally converting the film top surface into graphene, a graphene layer can be epitaxially formed on the Si substrates (graphene on silicon;GOS). In this method, epitaxial SiC thin films are first grown on the silicon substrate by using gas source molecular beam epitaxy. Normally, 3C-SiC(111), (110) and (100)-oriented films are grown on Si(111), (110) and (100) substrates, respectively. The surface of SiC thin films is then thermally graphitized by annealing at 1523 K in UHV to sublimate Si atoms. Not only 3C-SiC(111) but also (100) and (110) surfaces, produced epitaxial graphene as well. The Raman spectra show distinct D, G and G' bands for all these orientations. Synchrotron-radiation X-ray photoelectron spectrum of C1s presents sp$$^{2}$$ carbons atoms. The observation of the equally successful growth of graphene on these low-index SiC surfaces makes the GOS technology aviable in the post-Si device developments.

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