Bayesian estimation analysis of X-ray photoelectron spectra; Application to Si 2p spectrum analysis of oxidized silicon surfaces

Shinotsuka, Hiroshi*; Nagata, Kenji*; Yoshikawa, Hideki*; Ogawa, Shuichi*; Yoshigoe, Akitaka

Applied Surface Science, 685, p.162001_1 - 162001_11, 2025/03

https://doi.org/10.1016/j.apsusc.2024.162001

Silicon (Si) 2p photoelectron spectra of thermally oxidized Si(001) surfaces were analyzed using Bayesian estimation, a type of mathematical statistical processing, considering spin-orbit interactions. The accuracy of the estimation of fitting parameters and the model selection of the number of peaks were discussed. The spectral analysis was performed without any prior information on the positions of other Si peaks, except for the prominent bulk Si peak, and without using chemical-state assumptions. Our method completely verified previous findings on the surface species and the changes in peaks due to oxidation-induced strain as oxidation progressed.

Synchrotron radiation photoemission electron microscopy study on radioactive cesium-bearing microparticle collected in Fukushima

Yoshigoe, Akitaka; Tsuda, Yasutaka; Kobata, Masaaki; Okane, Tetsuo; Satou, Yukihiko; Okochi, Takuo*

e-Journal of Surface Science and Nanotechnology (Internet), 23(1), p.16 - 21, 2025/02

https://doi.org/10.1380/ejssnt.2025-004

Dissociative adsorption of supersonic CHCl on Cu oxide Surfaces; CuO(111) and bulk CuO precursor "29"; Structure on Cu(111)

Hayashida, Koki*; Tsuda, Yasutaka; Murase, Natsumi*; Yamada, Takashi*; Yoshigoe, Akitaka; Dio, W. A.*; Okada, Michio*

Applied Surface Science, 669, p.160475_1 - 160475_6, 2024/10

https://doi.org/10.1016/j.apsusc.2024.160475

In-situ X-ray imaging of the breakup dynamics of current-carrying molten metal jets during arc discharge

Sato, Yuriko*; Shobu, Takahisa; Tominaga, Aki; Sano, Tomokazu*; Ogino, Yosuke*

Communications Materials (Internet), 5, p.147_1 - 147_9, 2024/08

https://doi.org/10.1038/s43246-024-00586-1

The flow dynamics of current-carrying molten metal jet breakup during arc discharge serves as mass and heat sources in wire-arc-based metal deposition processes, thereby optimizing the resultant product quality. However, the spatiotemporal flow interaction between the molten metal jet and the surrounding arc plasma remains unclear. Here, using in-situ synchrotron X-ray imaging, we simultaneously track surface deformation and internal flow in molten aluminum jets during argon arc discharge. We reveal that modulating the magnitude and path of the arc discharge current can accelerate the jet velocity by 200 300% beyond its initial injection speed, thereby facilitating significant jet elongation. Our results provide consistent evidence that the jet flow dynamics are predominantly governed by the interaction between the arc discharge current and its coaxial self-induced magnetic field. This study establishes a framework at the intersection of fluid dynamics and electromagnetism, contributing to optimized control and precision in wire-arc-based applications.

Characterization of nitrided SiC(100) MOS structures by means of electrical measurements and X-ray photoelectron spectroscopy

Kobayashi, Takuma*; Suzuki, Asato*; Nakanuma, Takato*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Materials Science in Semiconductor Processing, 175, p.108251_1 - 108251_7, 2024/06

https://doi.org/10.1016/j.mssp.2024.108251

Crystal-like atomic arrangement and optical properties of 25LaO-75MoO binary glasses composed of isolated MoO

Masuno, Atsunobu*; Munakata, Sae*; Okamoto, Yoshihiro; Yaji, Toyonari*; Kosugi, Yoshihisa*; Shimakawa, Yuichi*

Inorganic Chemistry, 63(12), p.5701 - 5708, 2024/03

https://doi.org/10.1021/acs.inorgchem.4c00176

Transparent and brown LaO-MoO binary glasses were prepared in bulk form using a levitation technique. The glass-forming range was limited, with the primary composition being approximately 25 mol% LaO. This glass exhibited a clear crystallization at 546 C, while determining its glass transition temperature was difficult. Notably, despite its amorphous nature, the glass possessed a density and packing density comparable to those of crystalline LaMoO. X-ray absorption fine structure and Raman scattering analyses revealed that the glass structure closely resembles LaMoO due to the presence of isolated MoO units, whereas disordered atomic arrangement around La atoms was confirmed. The glass demonstrated transparency ranging from 378 to 5500 nm, and the refractive index at 1.0 m was estimated to be 2.0. The optical bandgap energy was 3.46 eV, which was slightly smaller than that of LaMoO. Additionally, the glass displayed a transparent region ranging from 6.5 to 8.0 m. This occurrence results from the decreased diversity of MoO units and connectivity of Mo-O-Mo, which resulted in the reduced overlap of multiphonon absorption. This glass formation, with its departure from conventional glass-forming rules, resulted in distinctive glasses with crystal-like atomic arrangements.

CHCl dissociation, CH abstraction, and Cl adsorption from the dissociative scattering of supersonic CHCl on Cu(111) and Cu(410)

Makino, Takamasa*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Dio, W. A.*; Okada, Michio*

Applied Surface Science, 642, p.158568_1 - 158568_6, 2024/01

https://doi.org/10.1016/j.apsusc.2023.158568

Depth concentration profile for cesium atom in fullerene C investigated using synchrotron X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Yaita, Tsuyoshi

Photon Factory Activity Report 2023 (Internet), 5 Pages, 2024/00

https://pfwww.kek.jp/acr/2023pdf/u_reports/pf23b0008.pdf

For nuclear transmutation of cesium-135 (Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom or CsI into fullerene (C) solid has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (ARXPS). It was found that Cs penetrates into C deep bulk. In contrast, CsI does not diffuse into bulk, although CsI over-layer was formed on the shallow surface. Furthermore, XPS spectra were measured as a function of Ar-sputtering time in order to know Cs concentration profiles in further deep region. Results showed that Cs penetrates into deep region of several hundreds .

Grasping behavior in metal under welding

Shobu, Takahisa

Kensa Gijutsu, 28(11), p.64 - 70, 2023/11

no abstracts in English

Automation of precise gas control for material-process researches; Application to synchrotron radiation real-time observation of surface reactions

Nakamura, Takafumi*; Yamamoto, Yukio*; Arakawa, Masakazu*; Maruyama, Akio*; Yoshigoe, Akitaka

Sangyo Oyo Kogakukai Rombunshi, 11(2), p.109 - 114, 2023/09

https://doi.org/10.12792/jjiiae.11.2.109

Surface chemistry experimental end-station at BL23SU in SPring-8 is widely used to study various surfaces and interfaces of functional materials by means of soft X-rays synchrotron radiation. To analyze surface chemical reactions between gas and solid surfaces, an accurate control of flow-rates of gases is essential. This paper describes a computerized automatic gas flow control system to improve the accuracy and reproducibility of gas-surface reaction experiments in the pressure range of ultra-high vacuum (molecular flow) conditions. The system uses feedback control to operate the slow-leak valve to control the gas-pressure. As a result, the system achieved results equivalent to those of a skilled experimenter.