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Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito
Vacuum and Surface Science, 66(9), p.525 - 530, 2023/09
As Au (001) surfaces exhibit a quasi-one-dimensional corrugated structure, Hex-Au(001), its periodicity was predicted to change the electronic structure of graphene when graphene was grown on this surface. Furthermore, the hybridization between graphene and Au is known to introduce bandgap and spin polarization into graphene. Here, we report angle-resolved photoemission spectroscopy and density functional theory calculation of graphene on a Hex-Au(001) surface. A bandgap of 0.2 eV in the graphene Dirac cone was observed at the crossing point of the graphene Dirac cone and Au 6sp bands, indicating that the origin of the bandgap formation was the hybridization between the graphene Dirac cone and Au 6sp band. We discussed the hybridization mechanism and anticipated spin injection into the graphene Dirac cone.
Yasuda, Satoshi; Di
o, W. A.*; Fukutani, Katsuyuki
Vacuum and Surface Science, 66(9), p.514 - 519, 2023/09
Monolayer graphene, representative of atomically thin crystals, has recently shown unexpectedly high proton and deuteron permeability under ambient conditions. It also permeates (filters) hydrogen (deuterium) isotope ion with high selectivity. These results suggest possible ways of developing novel and efficient hydrogen isotope gas enrichment techniques for manufacturing silicon semiconductors, optical fibers, drug development, nuclear fusion, and other related applications. And yet, despite its importance, experimental studies remain scarce and the separation mechanism contentious. Here, we introduce our recent findings on how quantum tunneling of hydrons through graphene could account for the high hydron selectivity of graphene.
(001) surface with supersonic seeded oxygen molecular beamKatsube, Daiki*; Ono, Shinya*; Inami, Eiichi*; Yoshigoe, Akitaka; Abe, Masayuki*
Vacuum and Surface Science, 65(11), p.526 - 530, 2022/11
The oxidation of oxygen vacancies at the surface of anatase TiO (001) was investigated by synchrotron radiation photoelectron spectroscopy and supersonic O beam (SSMB). The oxygen vacancies at the top surface and subsurface could be eliminated by the supply of hyperthermal oxygen molecules. Oxygen vacancies are present on the surface of anatase TiO(001) when it is untreated before transfer to a vacuum chamber. These vacancies, which are stable in the ambient condition, could also be effectively eliminated by using oxygen SSMB. This result is promising as a surface processing for various functional oxides.
on Pd(210)Ueta, Hirokazu; Fukutani, Katsuyuki
Vacuum and Surface Science, 64(9), p.430 - 434, 2021/09
Ogawa, Shuichi*; Taga, Ryo*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Journal of Vacuum Science and Technology A, 39(4), p.043207_1 - 043207_9, 2021/07
Times Cited Count：1 Percentile：7.86(Materials Science, Coatings & Films)Nickel (Ni) is used as a catalyst for nitric oxide decomposition and ammonia production but it is easily oxidized and deactivated. Clarification of the reduction process of oxidized Ni is essential to promote more efficient use of Ni catalysts. In this study, the reduction processes were investigated by in situ time-resolved photoelectron spectroscopy. We propose a two-step reduction reaction model. The rate-limiting process for the first step is surface precipitation of O atoms and that of the second step is dissociation of H molecules.
Ogawa, Shuichi*; Zhang, B.*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Vacuum and Surface Science, 64(5), p.218 - 223, 2021/05
The oxidation reaction kinetics on Ti(0001) and Ni(111) surfaces were observed by real-time photoelectron spectroscopy using synchrotron radiation to measure the oxidation state and oxide thickness. After the Ti(0001) surface was wholly covered by TiO with a thickness of 1.2 nm, the rapid growth of n-type TiO proceeded through the diffusion of Ti
ions to the TiO surface at 400
C. A saturation of oxygen uptake on the TiO surface indicates that the O sticking coefficient on the TiO surface is negligibly small and the segregation of Ti to the TiO surface is a trigger to initiate the TiO growth. On the Ni(111) surface at 350C, a thermally stable NiO
proceeded preferentially and then the growth of p-type NiO was initiated. The time evolution of NiO thickness was represented by a logarithmic growth model, where the NiO growth is governed by the electron tunneling to the NiO surface.
measurement and analysis techniques in X-ray photoelectron spectroscopy; From NAP-HARPES to 4D-XPSToyoda, Satoshi*; Yamamoto, Tomoki*; Yoshimura, Masashi*; Sumida, Hirosuke*; Mineoi, Susumu*; Machida, Masatake*; Yoshigoe, Akitaka; Suzuki, Satoru*; Yokoyama, Kazushi*; Ohashi, Yuji*; et al.
Vacuum and Surface Science, 64(2), p.86 - 91, 2021/02
We have developed measurement and analysis techniques in X-ray photoelectron spectroscopy. To begin with, time-division depth profiles of gate stacked film interfaces have been achieved by NAP-HARPES (Near Ambient Pressure Hard X-ray Angle-Resolved Photo Emission Spectroscopy) data. We then have promoted our methods to quickly perform peak fittings and depth profiling from time-division ARPES data, which enables us to realize 4D-XPS analysis. It is found that the traditional maximum entropy method (MEM) combined with Jackknife averaging of sparse modeling in NAP-HARPES data is effective to perform dynamic measurement of depth profiles with high precision.
optical microscopy of crystal growth of graphene using thermal radiationTerasawa, Tomoo; Taira, Takanobu*; Obata, Seiji*; Saiki, Koichiro*; Yasuda, Satoshi; Asaoka, Hidehito
Vacuum and Surface Science, 62(10), p.629 - 634, 2019/10
Graphene, an atomically thin sheet composed of sp
carbon atoms, has been the most attractive material in this decade. The fascinating properties of graphene are exhibited when it is monolayer. Chemical vapor deposition (CVD) is widely used to produce monolayer graphene selectively in large-area. Here we introduce "radiation-mode optical microscopy" which we have developed in order to realize the 
observation of the CVD growth of graphene. We show the method to observe graphene as bright contrast on Cu substrates in thermal radiation images. The growth mechanism, the nucleation site and rate limiting process, revealed by the observation is presented. Finally, we show the CVD growth of graphene on Au substrates, resulting in the tuning of the emissivity of graphene by the pre-treatment procedures. Our method is not only a way to observe the graphene growth but also shed light on the thermal radiation property of graphene.
Matsumoto, Masuaki*; Fukutani, Katsuyuki; 6 of others*
Journal of Vacuum Science and Technology A, 37(5), p.051601_1 - 051601_6, 2019/09
Times Cited Count：5 Percentile：27.67(Materials Science, Coatings & Films)Kamiya, Junichiro; Kinsho, Michikazu; Ogiwara, Norio*; Sakurai, Mitsuru*; Mabuchi, Takuya*; Wada, Kaoru*
Vacuum and Surface Science, 62(8), p.476 - 485, 2019/08
J-PARC 3GeV rapid cycling synchrotron (RCS) is one of the highest beam power proton accelerators. Challenges for achieving low pressure region in ultra-high vacuum (UHV) in the beam line are the large outgassing source. We focused turbo molecular pumps (TMP) as maing pump because it can evacuate the continuous and additional outgassing with large pumping speed in wide pressure range. It is also possible to evacuate from low vacuum to UHV with only a few hours by using TMP, which ensures users' experimental time after vacuum device maintenance. During more than 10 years operation of the vacuum system, many experiences have been accumulated about the usage of TMP in RCS. In this presentation, we discussed about validity of TMP as main pump in high power proton beam accelerator by showing the performance of the beam line pressure during the beam operation. Further, in anticipation of upgrade higher beam power more than 1 MW, validity of a combination of TMP and NEG pump will be mentioned.
Yamada, Ippei; Ogiwara, Norio*; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu
Vacuum and Surface Science, 62(7), p.400 - 405, 2019/07
no abstracts in English
Ogawa, Shuichi*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Vacuum and Surface Science, 62(6), p.350 - 355, 2019/06
Thermal oxidation of Si substrate is an indispensable process for the Si device fabrication. However, the influence of oxidation induced strain cannot be ignored for thin films. Synchrotron radiation real-time photoelectron spectroscopy was used as a method to measure simultaneously oxidation induced strain and oxidation rate. It was found that the acceleration of interfacial oxidation induced by thermal strain was observed for the rapid thermal oxidation. The results can be explained by the model in which point defects caused by strain become reaction sites at the SiO/Si interface.
Hasegawa, Yuri; Yamada, Yoichi*; Sasaki, Masahiro*
Vacuum and Surface Science, 61(6), p.366 - 371, 2018/06
Molecular arrangements and electronic states of well-ordered (DNTT) and picene thin film on single crystal were measured by means of scanning tunneling microscope (STM) and angle-resolved photoemission spectroscopy, respectively. DNTT and picene form single crystalline-like molecular arrangement on inert Au(111) substrate. Splitting of HOMO energy due to overlapping with adjacent molecules was suggested by ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculation. On the other hand, one-dimensional ordering of those molecule was observed on anisotropic Ag(110) substrate. However, the HOMO band dispersion was found to be 200 meV at maximum, showing that the overlapping of HOMO was smaller in such arrangement comparing with that in their single crystal.
Kamiya, Junichiro; Kinsho, Michikazu; Abe, Kazuhiko*; Higa, Kyusaku*; Koizumi, Oji*
Journal of Vacuum Science and Technology A, 36(3), p.03E106_1 - 03E106_10, 2018/05
Times Cited Count：0 Percentile：0.01(Materials Science, Coatings & Films)The 3 GeV Rapid Cycling Synchrotron (RCS) in J-PARC aims to generate one of the highest power protons in the world, whose design extraction beam power is 1 MW. Beam pipes of alumina ceramics are used to prevent the induced current, which is caused by the rapid change of the magnetic field. In the beam injection section, ceramics beam pipes for a quadrupole magnet and a horizontal shift bump magnet are connected without bellows due to the very limited space. To improve maintainability, the ceramics beam pipes for the quadrupole magnet were newly designed to insert the bellows. We will report the design concept of the new alumina ceramics beam pipes with low spring constant bellows and the several results of the verification tests.
Kamiya, Junichiro; Kinsho, Michikazu; Yamazaki, Yoshio; Yoshimoto, Masahiro; Yanagibashi, Toru*
Journal of the Vacuum Society of Japan, 60(12), p.484 - 489, 2017/12
Multi-turn H
charge exchange injection is employed as a beam injection method in the 3-GeV RCS (Rapid cycling synchrotron) at J-PARC (Japan Proton Accelerator Research Complex). In this method, injection H beam is put on the same orbit as already circulating proton (H
) beam in a dipole magnetic field due to the opposite curvature of the injected and circulating beams. In the straight section, where the two beams coincide with each other, both beams are passed through a thin foil, which strips two weakly bound electrons off each H ion, forming an intense beam of protons. The thin foil, which is mostly made of carbon, would be the source of the outgassing, especially when its temperature rises due to the beam hitting. Therefore it is important to estimate the amount and components of the outgassing from the charge stripping foil. In this paper, we will report the thermal desorption measurement results for the several foil, which is used as the charge stripping foil in the RCS.
Ogiwara, Norio; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu; Yoshida, Hajime*; Arai, Kenta*
Journal of the Vacuum Society of Japan, 60(12), p.475 - 480, 2017/12
Morishita, Takatoshi; Kondo, Yasuhiro; Oguri, Hidetomo; Hasegawa, Kazuo
Journal of Vacuum Science and Technology A, 35(4), p.041602_1 - 041602_5, 2017/07
Times Cited Count：1 Percentile：4.92(Materials Science, Coatings & Films)In the J-PARC, the linac provides 400 MeV hydrogen negative ion beam to the following 3GeV synchrotron. For the beam current upgrade, the new radio-frequency quadrupole (RFQ) linac, in which the design peak beam current was increased from 30 to 50 mA, has been fabricated and installed in the beam line in summer 2014. The beam provision to users started in the beginning of November, 2014. Since then, the RFQ operates without serious problems for more than two years, however, the operation stability of the RFQ with beam acceleration was not enough due to the sparking in the cavity. We consider that the impurities in the vacuum chamber are related to this sparking phenomena. The design and performance of the RFQ vacuum system is described in this paper, then, the relationship among the sparking rates, the residual gas species in the vacuum chamber, and the beam operation parameters are described.
Kamiya, Junichiro
Journal of the Vacuum Society of Japan, 59(8), p.213 - 221, 2016/08
Basic role of the vacuum systems in conventional particle accelerators is to maintain enough low pressure in the beam lines to guarantee the beam lifetime. In high power proton beam accelerators, the requirement for the vacuum system is much tougher due to the large size vacuum devices and high radioactivation. In addition, it is essential to pre-treat the vacuum materials in order to suppress pressure instability due to gas desorption from the vacuum wall originating from the large amount of the charged particles. Further, the rapid evacuation from the atmospheric pressure to the UHV after maintenance is also required to ensure the beam operation time. We aim to present the typical vacuum technologies in high power proton beam accelerator by introducing the vacuum system of J-PARC, especially of 3GeV rapid cycling synchrotron (RCS).
Ogiwara, Norio; Hikichi, Yusuke; Kamiya, Junichiro; Kinsho, Michikazu
Journal of the Vacuum Society of Japan, 59(4), p.79 - 82, 2016/04
baking method for degassing of a kicker magnet in accelerator beam lineKamiya, Junichiro; Ogiwara, Norio; Yanagibashi, Toru*; Kinsho, Michikazu; Yasuda, Yuichi*
Journal of Vacuum Science and Technology A, 34(2), p.021604_1 - 021604_10, 2016/03
Times Cited Count：3 Percentile：14.94(Materials Science, Coatings & Films)In this study, we propose a new 
degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted heat expansion of the chamber. The bake-out system comprises the heater and thermal radiation shield plates, which are installed between the kicker magnet and the chamber wall. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. A graphite heater was selected in this application to bake-out the kicker magnet in the beam line to ensure reliability and easy maintainability of the heater. The vacuum characteristics of graphite were suitable for heater operation in the beam line. A preliminary heat-up test conducted in the accelerator beam line also showed that each part of the kicker magnet was successfully heated and that heat expansion of the chamber was negligibly small.
