e-Journal of Surface Science and Nanotechnology
Online ISSN : 1348-0391
ISSN-L : 1348-0391
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Displaying 1-15 of 15 articles from this issue
  • Kensuke Shirode, Hitoshi Kawai, Hiroaki Oe, Shinya Yagi
    Article type: Regular Paper
    Subject Area: Structure
    Article ID: 2023-025
    Published: March 11, 2023
    Advance online publication: March 11, 2023
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    Here, we develop a technique for curve-fitting of the sulfur K-edge near-edge X-ray absorption fine structure (NEXAFS) to analyze the crosslinked structure of vulcanized rubber based on the chemical state of sulfur. The proposed analytical method provides the sulfur chain length (Sx), crosslink density, and sulfur oxide content simultaneously, and it is highly sensitive for the analysis of the depth direction. Furthermore, we verify the aging mechanism of the crosslinked structure using this analytical method. It is found that the sulfur chains, shortened and oxidized by heat aging at 120°C, can cause scission of the S—C bond, thereby decreasing the crosslink density. Long sulfur chains are more susceptible to oxidation, which rapidly decreases the sulfur chain length (Sx) and, in turn, the crosslink density compared with short sulfur chains. By comparing the heat-aging dependence between the S—C bond and S100, it is found that the styrene-butadiene rubber polymer surface can form the C—C crosslink. We present the aging mechanism of the crosslinked structure and establish NEXAFS as a useful analytical method for rubber materials.

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  • Daiki Kido, Takahiro Wada, Kiyotaka Asakura
    Article type: Proceeding Paper
    Subject Area: Catalysis
    Article ID: 2023-026
    Published: March 11, 2023
    Advance online publication: March 11, 2023
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    The thorough search (TS) method was introduced to solve the problems in a conventional extended X-ray absorption fine structure analysis method. The TS method gives all possible and rational structures (structure candidates) which can reproduce the experimental data well in the parameter space. However, it still has difficulties how to decide the number of structure candidates without discretion and visualize the parameter sets with dimensions of more than 3. In this paper, we have applied the K-means method and principal component analysis and discussed its merits and drawbacks.

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  • Osamu Endo, Fumihiko Matsui, Satoshi Kera, Wang-Jae Chun, Masashi Naka ...
    Article type: Proceeding Paper
    Subject Area: Electronic Properties
    Article ID: 2023-024
    Published: March 09, 2023
    Advance online publication: March 09, 2023
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    Photoemission spectroscopy of the perylene layers on the Au(110) surface was performed using a momentum microscope. The two-dimensional momentum maps of the perylene monolayer exhibit a “binary star” pattern with two asymmetric bright spots for the electrons from the highest occupied molecular orbital of perylene, reflecting the tilted molecular orientation. This pattern was absent for the perylene multilayer and the Br-doped monolayer because of the random orientation of the molecules in these layers. Br doped to the perylene monolayer facilitated hole injection in perylene, and the electrons attributable to the singly occupied molecular orbital were observed at binding energies of 1.0—1.5 eV.

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  • Satoka Aoyagi, Daisuke Hayashi, Yoshiharu Murase, Naoya Miyauchi, Akik ...
    Article type: Superexpress Letter
    Subject Area: Structure
    Article ID: 2023-023
    Published: February 25, 2023
    Advance online publication: February 25, 2023
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    Supplementary material

    Electron backscatter diffraction (EBSD) indexing based on Kikuchi diffraction patterns, which indicate the types and orientation of the crystal lattice, is effective for characterizing crystals. Most regions in a sample can be indexed due to simulation of diffraction patterns of possible crystal types, orientations, and angles. However, indexing some of the complex regions related to the grain boundaries, dislocations, and strain areas is difficult. Moreover, minor crystal structures are possibly omitted from the index results. To characterize all the regions, including such complicated boundaries, the analysis of raw data, including all Kikuchi patterns, is necessary. By analyzing all the Kikuchi patterns, significant information can be extracted from mixed crystal conditions. Stainless steel was used as the model sample in this study. As hydrogen diffusion in metals strongly depends on the crystal structure and grain boundaries, structural analysis is required to study hydrogen behavior in steel. In this study, all Kikuchi patterns at all pixels in a measurement area of stainless steel were analyzed simultaneously using unsupervised learning methods, such as principal component analysis and multivariate curve resolution, and the pixels of the measurement area were classified based on the Kikuchi patterns to investigate the grain boundaries and dislocations in detail.

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  • Masato Mori, Xiaobin Liang, Ken Nakajima
    Article type: Proceeding Paper
    Subject Area: Nano-Science and -Technology
    Article ID: 2023-022
    Published: February 23, 2023
    Advance online publication: February 23, 2023
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    Atomic force microscope (AFM)-based single molecular force spectroscopy has been widely used to study the mechanical properties of polymers. In recent years, the development of dynamic force spectroscopy of single polymer chains has enabled us to measure the viscoelasticity of polymers. In this paper, we report the direct measurement of viscoelasticity of a single polystyrene (PS) chains in N,N-dimethyl formamide by using thermal noise analysis. This technique does not require any vibration of AFM cantilever and allows polymer chains to be measured near-equilibrium conditions. Furthermore, we evaluated the force-dependences of the elasticity and viscosity for a single PS chain. The elastic behaviors of single molecular chains were well described with the worm-like chain model in the high-stretch region. However, this model cannot provide an assessment of viscous behavior because the responses of the single polymer chain to the cantilever were so small that those were hidden by the cantilever’s response to the system. To improve the measurement accuracy of the viscous behavior, we fabricated for the first time high-tip cantilever by a focused ion-beam processing, by which the hydrodynamic effect between the cantilever and substrate was reduced.

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  • Hiroshi Ando, Masafumi Horio, Yoko Takeo, Masahito Niibe, Tetsuya Wada ...
    Article type: Technical Note
    Subject Area: Instrumentations and Techniques
    Article ID: 2023-020
    Published: February 18, 2023
    Advance online publication: February 18, 2023
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    We developed a compact system for the spectroscopic mapping of a microstructure with a nano-focused beam at a soft X-ray beamline of synchrotron radiation. The experimental setup comprises a Wolter mirror and sample that are arranged with two mounting stages. The Wolter mirror is aligned with three degrees of freedom, and the sample with two degrees. The system generates a beam with an 800-nm spot and maps out a chemical distribution of non-uniform material through near-edge X-ray fine structure spectroscopy. The design and actual system are suited to experiments conducted with a nano-focused X-ray beam at beamlines of synchrotron radiation or an X-ray free-electron laser. Additionally, this technical note presents guidelines for actual experiments.

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  • Takahiko Satake, Hiroharu Kawasaki, Shin-ichi Aoqui
    Article type: Proceeding Paper
    Subject Area: Thin Films
    Article ID: 2023-021
    Published: February 18, 2023
    Advance online publication: February 18, 2023
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    A composition-controlled functional film preparation method by plasma process using powder mixture targets. Thin films of a mixture of titanium (Ti) and stainless steel (SUS), which is known as a metal that affords a high rate of hydrogen penetration, were prepared using mixture powder targets of titanium oxide (TiO2) and SUS in this study. Experimental results indicated that titanium and SUS mixture thin films were successfully prepared, and their mixtures could be controlled both on the SUS and Si substrate surface. In addition, the mixture of the TiO2 and SUS powders in the target strongly affects surface morphology and/or crystallinity in the produced functional thin film. Gradient-functional thin films were prepared using 11 powder targets with variable Ti and Fe compositions. X-ray photoelectron spectroscopy depth profile results suggest that the Ti and Fe composition gradient thin films can be prepared by sputtering with mixed powder targets.

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  • Akane Iida-Adachi, Hideki Nabika
    Article type: Regular Paper
    Subject Area: Bio-Science and -Technology
    Article ID: 2023-019
    Published: January 19, 2023
    Advance online publication: January 19, 2023
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    Understanding the behavior of individual amyloid β (Aβ) monomers, oligomers, and aggregates is important to elucidate the cause of Alzheimer's disease, which has many unsolved mechanistic aspects. In this study, we focused on the behavior of characteristic individual Aβ monomers, oligomers, and fibrils, which were observed using total internal reflection fluorescence microscopy (TIRFM). Specifically, TIRFM enabled observing how each Aβ species adsorbs, aggregates, and diffuses on a lipid membrane. This study, thus, offers a more precise understanding of the dynamic behavior of Aβ on lipid membranes by matching the number of molecules contained in each association with individual Aβ behavior. By tracking the time-course of fluorescence intensities derived from Aβ, the fluorescence intensity of a single Aβ molecule was identified. The diffusivity of Aβ on a lipid membrane revealed that Aβ monomers and oligomers do not always diffuse at a constant rate, but rather change from mobile to immobile and from immobile to mobile states, depending on the number of associations. The adsorption and desorption of Aβ were also observed. Simultaneous observation of fluorescence intensity and diffusivity of each oligomer revealed disassembly from a hexamer to two trimers, followed by desorption of one trimer while the other trimer remains on the membrane. Although the Aβ aggregate was partially adsorbed on the membrane, the non-adsorbed portion was free to move. These results provide new insights and an updated method to gain a better understanding of the aggregation process of Aβ and its contribution to Alzheimer's disease.

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  • Kotaro Takeyasu, Yuta Katane, Naoto Miyamoto, Mo Yan, Junji Nakamura
    Article type: Regular Paper
    Subject Area: Catalysis
    Article ID: 2023-018
    Published: December 28, 2022
    Advance online publication: December 28, 2022
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    Mixed-potential-driven catalysis could be a novel strategy to control catalytic selectivity. In this mechanism, anodic and cathodic reactions occur simultaneously, forming a mixed potential on the nano-anode and nano-cathode composed of a supported catalyst. To prove the mixed-potential-driven catalysis, we developed a new model reactor with separated electrodes to directly measure currents between anodic and cathodic reactions under high-pressure conditions. We observed that reaction currents supported mixed-potential reactions only when a CO2/H2 mixture was introduced into the model reactor with Cu and Pd electrodes without separating CO2 and H2. This indicates that CO2 reduction and H2 oxidation occurred simultaneously on the Cu and Pd catalysts, respectively, based on the catalytic activity via the mixed-potential mechanism. The products of reaction for 18 h at 373 K were CO, methanol, and ethanol.

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  • Zizhan Sun, Xiaoyu Wang, Feihu Tao, Xu Zhang, Lizhai Pei
    Article type: Regular Paper
    Subject Area: Nano-Materials
    Article ID: 2023-017
    Published: December 22, 2022
    Advance online publication: December 22, 2022
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    Supplementary material

    Rare metal (La or Nd) doped BaSn-based composites with highly polycrystalline nature were successfully synthesized through a simple hydrothermal route. The doped composites were investigated by X-ray diffraction, electron microscopy, solid ultraviolet diffuse reflectance spectrum, X-ray photoelectron spectroscopy, photoluminescence, electrochemical impedance spectroscopy, and photocatalytic measurements. La and Nd doping induces the morphological change of the BaSn-based composites from the nanorods to irregular nanoscale particles with the average size of about 100 nm. La and Nd in the doped composites exist in the form of cubic La2Sn2O7 and cubic Nd2Sn2O7 phases. The absorption edge of the doped composites red-shifts comparing with that of the non-doped composites. The doped BaSn-based composites with the La or Nd mass ratio of 8 wt% possess the smallest band-gap energy in the doped composites and the good light absorption ability. The La or Nd doping mass ratio has an important role in the photocatalytic degradation of the crystal violet (CV) dye. The CV molecules in the 20-mL CV solution with 10 mg L−1 can be totally removed by the 20-mg La- or Nd-doped BaSn-based composites under the light irradiation for 150 min. Scavenger experiments show that hydroxyl free radicals (·OH) and superoxide anion radicals (·O2) are effective oxidizing agents for CV degradation. Photoluminescence and electrochemical impedance spectroscopy show that the significant decrease in the recombination ability of the electron and hole pairs by the rare metal doping is of great importance for enhancing the photocatalytic activity of the BaSn-based composites. The La- or Nd-doped BaSn-based composites show good reusability for CV degradation.

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  • Junichiro Kamiya, Kazuhiro Takano, Kaoru Wada, Toru Yanagibashi
    Article type: Regular Paper
    Subject Area: Vacuum
    Article ID: 2023-015
    Published: December 10, 2022
    Advance online publication: December 10, 2022
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    Vacuum firing, which is a heat treatment at high temperature in a high vacuum furnace, is known as the method for the outgassing reduction of the vacuum materials, such as stainless steel, titanium, etc. The outgassing rate of the vacuum-fired stainless steel is known to be low after ordinal baking at 150−200°C, which is typically in the order of 10−11−10−10 Pa m3 s−1. In this research, the effect of the vacuum firing (850°C for 10 h) on the stainless steel SUS304 is investigated from the vacuum and surface point of view. The build-up test of the stainless steel vacuum chamber clearly showed the outgassing suppression by the vacuum firing. Especially, the hydrogen outgassing, which was the main component after baking, was much reduced. Thermal desorption spectroscopy showed that the vacuum firing reduced the desorption of H2, H2O, CO, and CO2 with high desorption energy even after air exposure. Especially, the effect on H2 was very large. X-ray photoelectron spectroscopy (XPS) showed the increase of ferric oxide and the decrease of chrome oxide on the near surface of the vacuum-fired stainless steel. On the other hand, XPS also showed that the chrome oxide was systematically increased by heating from 200 to 400°C. These results support the outgassing reduction mechanism by the vacuum firing that the hydrogen is reduced from the bulk due to the diffusion to the vacuum phase during the vacuum firing and the surface metal oxides are reformed as a diffusion barrier from the gas phase to the bulk.

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  • Yukichi Shigeta, Morio Higuchi, Yuto Hagiwara
    Article type: Proceeding Paper
    Subject Area: Structure
    Article ID: 2023-014
    Published: December 10, 2022
    Advance online publication: December 10, 2022
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    The Kikuchi pattern gives a lot of information about diffracted waves under different incident conditions, because the pattern forms by inelastic scattered electrons having various directions. By analyzing the intensity of the pattern, information equivalent to the results measured under many incident conditions can be obtained. To analyze the Kikuchi pattern, it is necessary to know the inelastic scattering cross-section. As a first step, we estimated “apparent” inelastic scattering cross-section in the Kikuchi pattern by comparing it with the results of dynamic diffraction intensity calculation. In the formation of the Kikuchi patterns, although phonons and bulk plasmons mainly contribute to the Kikuchi lines, it has been suggested that surface plasmons have a significant influence on the Kikuchi envelope.

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  • Yoshimu Iwanami, Nobuharu Kimura, Kazuo Tagawa, Satoshi Yasuno
    Article type: Proceeding Paper
    Subject Area: Thin Films
    Article ID: 2023-016
    Published: December 10, 2022
    Advance online publication: December 10, 2022
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    The fuel-saving performance of automotive lubricants greatly depends on the composition and chemical structure of the reaction films that form on metal surfaces through chemical reactions between the additives in the lubricant and the metals. In this study, we prepared four kinds of reaction film on metal surfaces using lubricants formulated with ZnDTP only or with ZnDTP and MoDTC and then investigated the relationship between the lubricant formulations and the chain lengths of polyphosphates in the reaction films by angle-resolved HAXPES. The chain lengths of polyphosphates were estimated by the O1s spectra. We found that the polyphosphate chains in the reaction films formed by ZnDTP and MoDTC were shorter than those in the films formed by ZnDTP only, regardless of the length of the ZnDTP’s alkyl group. We also found that films formed by ZnDTP with a shorter alkyl group had longer polyphosphate chains, regardless of whether MoDTC was also present.

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  • Masayuki Mori, Jotaro Inoue, Koichi Maezawa
    Article type: Regular Paper
    Subject Area: Thin Films
    Article ID: 2023-012
    Published: December 08, 2022
    Advance online publication: December 08, 2022
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    The heteroepitaxial growth of InGaSb films via indium- and/or gallium-induced surface reconstruction on a Si(111) substrate was carried out by using surface reconstruction controlled epitaxy method in an ultra-high vacuum chamber. The influence of the composition ratio of the InGaSb bi-layer on the growth of the InGaSb films was studied. To find the growth condition for the 30°-rotated InGaSb films without twin, the composition ratio of In and Ga atoms of the initial InGaSb bi-layer on Si(111) surface was varied from 10 : 0 to 2 : 8 under the condition in which the composition ratio of the InGaSb films is fixed. The 30°-rotated InGaSb film with respect to the Si substrate was able to grow on the InSb bi-layer, but it showed a twin nature of the film. On the InGaSb bi-layer with the higher In composition ratio, the InGaSb films tend to form twins. On the other hand, InGaSb grown on the InGaSb bi-layer with the higher Ga composition does not rotate with respect to Si surface and has few twins. The structure of the InGaSb films is affected by the composition ratio of the underlying InGaSb bi-layer and by the composition ratio of the film. We could narrow down the range of growth conditions requited to grow 30°-rotated InGaSb films without twins in this study.

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  • Hiroaki Tanaka
    Article type: Regular Paper
    Subject Area: Electronic Properties
    Article ID: 2023-013
    Published: December 08, 2022
    Advance online publication: December 08, 2022
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    Based on the first-order perturbation theory, we show that the wave function of a photoelectron is a wave packet with the same width as the incident light pulse. Photoelectron detection measurements revealed that the widths of signal pulses were much shorter than the light pulse and independent of the origin (photoemission or other noises), which is an experimental observation of the wave function collapse. Signal pulses of photoelectrons were distributed along the time axis within the same width as the light pulse, consistent with the interpretation of a wave function as a probability distribution.

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