Investigation of niobium surface roughness and hydrogen content with different polishing conditions for performance recovery of superconducting QWRs in JAEA Tokai-Tandem Accelerator

Kamiya, Junichiro; Nii, Keisuke*; Kabumoto, Hiroshi; Kondo, Yasuhiro; Tamura, Jun; Harada, Hiroyuki; Matsui, Yutaka; Matsuda, Makoto; Moriya, Katsuhiro; Ida, Yoshiaki*; et al.

e-Journal of Surface Science and Nanotechnology (Internet), 6 Pages, 2023/05

https://doi.org/10.1380/ejssnt.2023-046

no abstracts in English

Evaluation of doped potassium concentrations in stacked two-Layer graphene using real-time XPS

Ogawa, Shuichi*; Tsuda, Yasutaka; Sakamoto, Tetsuya*; Okigawa, Yuki*; Masuzawa, Tomoaki*; Yoshigoe, Akitaka; Abukawa, Tadashi*; Yamada, Takatoshi*

Applied Surface Science, 605, p.154748_1 - 154748_6, 2022/12

https://doi.org/10.1016/j.apsusc.2022.154748

Immersion of graphene in KOH solution improves its mobility on SiO/Si wafers. This is thought to be due to electron doping by modification with K atoms, but the K atom concentration C in the graphene has not been clarified yet. In this study, the C was determined by XPS analysis using high-brilliance synchrotron radiation. The time evolution of C was determined by real-time observation, and the C before irradiation of synchrotron radiation was estimated to be 0.94%. The C 1s spectrum shifted to the low binding energy side with the desorption of K atoms. This indicates that the electron doping concentration into graphene is decreasing, and it is experimentally confirmed that K atoms inject electrons into graphene.

Observation of chemisorbed O molecule at SiO/Si(001) interface during Si dry oxidation

Tsuda, Yasutaka; Yoshigoe, Akitaka; Ogawa, Shuichi*; Sakamoto, Tetsuya*; Takakuwa, Yuji*

e-Journal of Surface Science and Nanotechnology (Internet), 21(1), p.30 - 39, 2022/11

https://doi.org/10.1380/ejssnt.2023-005

Annealing effect of absorbing property for Cs and CsI in fullerene investigated by synchrotron X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Yaita, Tsuyoshi

e-Journal of Surface Science and Nanotechnology (Internet), 20(3), p.186 - 195, 2022/07

https://doi.org/10.1380/ejssnt.2022-030

Cesium-135 having long life, 2.3 million y, that is contained in nuclear wastes may cause long-term pollution. Technology of isotopic separation of such long lived nuclide is indispensable not only for its volume reduction but also annihilation by nuclear transmutation. The recovery of atomic Cs from molecular CsI is mandatory. We have investigated fullerene C as a potential absorber for Cs. Angle-resolved X-ray photoelectron spectroscopy, AR-XPS has been used to analyze the depth concentration distribution of Cs. Experiments were performed at soft X-ray beamline BL27A at KEK PF facility. We report on the annealing effect after deposition of Cs and the effect of heating substrate during deposition. For Cs/C sample, the intensity ratio of Cs-3d/C-1s increased in double at the high temperature. This suggests that Cs atoms remain in the material at high temperatures. On the other hand, for CsI/C, the intensity ratio does not change much by elevating temperatures.

Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; Koitaya, Takanori*; Yamamoto, Susumu*; Namba, Yusuke*; Song, C.*; Kim, J.*; Yoshigoe, Akitaka; Koyama, Michihisa*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06

https://doi.org/10.1016/j.apsusc.2022.152797

The hydrogen absorption and diffusion mechanisms on cube-shaped Pd nanoparticles (NPs) which are important hydrogen-storage materials were studied using X-ray photoelectron spectroscopy and DFT calculations. In the surface region, hydrogen absorption showed almost similar behavior regardless of the NPs size. It was found that the octahedral sites are more favorable than the tetrahedral sites for hydrogen occupation. We also clarified that the hydrogen atoms absorbing on the smaller-sized Pd NPs diffuse to the subsurface more actively because of the weakened Pd-H bond by the surface disordering, which plays an important role in hydrogen adsorption at a low H pressure.

Evaluation of titanium vacuum chamber as getter pump

Kamiya, Junichiro; Takano, Kazuhiro*; Yuza, Hiromu*; Wada, Kaoru

e-Journal of Surface Science and Nanotechnology (Internet), 20(2), p.107 - 118, 2022/05

https://doi.org/10.1380/ejssnt.2022-017

no abstracts in English

Ultrafast surface Dirac fermion dynamics of SbTe-based topological insulators

Sumida, Kazuki; Ishida, Yukiaki*; Gdde, J.*; Hfer, U.*; Shin, S.*; Kimura, Akio*

Progress in Surface Science, 96(2), p.100628_1 - 100628_15, 2021/05

https://doi.org/10.1016/j.progsurf.2021.100628

Synchrotron X-ray standing wave Characterization of atomic arrangement at interface between transferred graphene and -AlO(0001)

Entani, Shiro*; Honda, Mitsunori; Naramoto, Hiroshi*; Li, S.*; Sakai, Seiji*

Surface Science, 704, p.121749_1 - 121749_6, 2021/02

https://doi.org/10.1016/j.susc.2020.121749

Graphene is expected to be one of the most promising materials for nanoelectronics and spintronics. In most graphene-based devices, the graphene channel is placed on insulating substrates. Therefore, the study of inter-facial interactions between graphene and the insulator surface is of critical importance. In this study, the vertical arrangement of graphene which is transferred on -AlO(0001) has been studied by normal incidence X-ray standing wave (NIXSW) technique. The analysis of the NIXSW profile reveals that the graphene layer is located at 3.57 () above the -AlO(0001) surface, which is larger than the interlayer distance of graphite at 3.356 (). Micro- Raman spectroscopy shows that the transferred graphene has a limited spatial distribution of hole concentration. The present study shows that transferred graphene on the sapphire substrate followed by vacuum-annealing has an atomically flat surface free from residual contaminations such as organic compounds and there occurs the hole-doping in graphene.

Precise chemical state analyses of ultrathin hafnium films deposited on clean Si(111)-77 surface using high-resolution core-level photoelectron spectroscopy

Kakiuchi, Takuhiro*; Matoba, Tomoki*; Koyama, Daisuke*; Yamamoto, Yuki*; Kato, Daiki*; Yoshigoe, Akitaka

Surface Science, 701, p.121691_1 - 121691_8, 2020/11

https://doi.org/10.1016/j.susc.2020.121691

Ultrathin hafnium films on Si(111)-77 were studied using synchrotron radiation photoelectron spectroscopies to reveal the chemical states at interface and surface. Ultrathin Hf layers grow on clean Si(111)-77 surface by lever rule. Surface and interface of Hf/Si(111) contain three components (metallic Hf layers, Hf monosilicide (HfSi) and Si-rich Hf silicide). Ultrathin Hf layers changes HfSi islands on bared Si(111)-77 surface after annealing at 1073 K. It was found that the long axes of the rectangle islands expand the direction connecting the corner holes in DAS model of clean Si(111)-77 surface.

Initial oxidation processes of ultrathin hafnium film and hafnium disilicide islands on Si(100)-21 surfaces studied using core-level X-ray photoelectron spectroscopy

Kakiuchi, Takuhiro*; Yamasaki, Hideki*; Tsukada, Chie*; Yoshigoe, Akitaka

Surface Science, 693, p.121551_1 - 121551_8, 2020/03

https://doi.org/10.1016/j.susc.2019.121551

We investigated the initial oxidation of ultrathin hafnium (Hf) film on Si(100)-21 using photoelectron spectroscopy. Metallic Hf rapidly oxidized, transforming into hafnium dioxide (HfO) and its suboxides. The other HfSi component at the interface was nearly unreactive with O molecules. These facts suggest that the metallic Hf component plays a vital role in the initial oxidation of the ultrathin Hf/Si(100) film. After annealing from 873 K to 973 K, the Hf suboxides in low ionic valences progressed into fully oxidized HfO. Once the annealing temperature reached c.a.1073 K, oxygen atoms were entirely removed from the ultrathin HfO/Si(100) film containing SiO at the interface. Simultaneously, ultrathin HfO layers changed into islands of Hf disilicide (-HfSi) on a bare Si(100)-21 surface. The -HfSi component showed slight reactivity with O molecules at 298 K. In contrast to the initial oxidation of clean Si(100)-21 surface, the dangling bonds on bare Si(100)-21 surface among -HfSi oxidized preferentially.