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Journal Articles

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

 Times Cited Count:0 Percentile:0.01(Chemistry, Physical)

Immersion of graphene in KOH solution improves its mobility on SiO$$_{2}$$/Si wafers. This is thought to be due to electron doping by modification with K atoms, but the K atom concentration C$$_{K}$$ in the graphene has not been clarified yet. In this study, the C$$_{K}$$ was determined by XPS analysis using high-brilliance synchrotron radiation. The time evolution of C$$_{K}$$ was determined by real-time observation, and the C$$_{K}$$ 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.

Journal Articles

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

 Times Cited Count:4 Percentile:91.83(Chemistry, Physical)

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$$_{2}$$ pressure.

Journal Articles

Mass transport in the PdCu phase structures during hydrogen adsorption and absorption studied by XPS under hydrogen atmosphere

Tang, J.*; Yamamoto, Susumu*; Koitaya, Takanori*; Yoshigoe, Akitaka; Tokunaga, Takuma*; Mukai, Kozo*; Matsuda, Iwao*; Yoshinobu, Jun*

Applied Surface Science, 480, p.419 - 426, 2019/06

 Times Cited Count:9 Percentile:54.8(Chemistry, Physical)

Mass transports during hydrogen adsorption and absorption processes of PdCu alloys that has advantages of higher hydrogen diffusivity and economically lower-cost than the other Pd-alloys were studied. The research was made with a comparison of the well-known ordered phase of the bcc structure (the B2 phase) and a mixed phase of the fcc and B2 structures. ${it In-situ}$ ultrahigh vacuum X-ray photoelectron spectroscopy and ambient pressure X-ray photoelectron spectroscopy using synchrotron radiation were carried out to trace the chemical states of the Pd and Cu atoms as a function of temperatures. It is elucidated that the initial adsorption and absorption processes were similar in the two phases, but a hydrogen diffusion rate to the bulk was higher in the ordered phase than in the mixed one. We found the dynamics of the Pd and Cu atoms during the hydrogen adsorption/absorption processes largely depend on temperature. In the hydrogen atmosphere, the Pd atoms segregate at the surface below 373 K and Cu atoms segregate at the surface above 373 K. The present results agree well with the previous theoretical calculations and, thus, provide appropriate inputs toward developments of the hydrogen permeation materials.

Journal Articles

In situ X-ray observations of pure-copper layer formation with blue direct diode lasers

Sato, Yuji*; Tsukamoto, Masahiro*; Shobu, Takahisa; Funada, Yoshinori*; Yamashita, Yorihiro*; Hara, Takahiro*; Sengoku, Masanori*; Sakon, Yu*; Okubo, Tomomasa*; Yoshida, Minoru*; et al.

Applied Surface Science, 480, p.861 - 867, 2019/06

 Times Cited Count:20 Percentile:79.78(Chemistry, Physical)

Journal Articles

Micro-orientation control of silicon polymer thin films on graphite surfaces modified by heteroatom doping

Shimoyama, Iwao; Baba, Yuji; Hirao, Norie*

Applied Surface Science, 405, p.255 - 266, 2017/05

 Times Cited Count:1 Percentile:6.72(Chemistry, Physical)

NEXAFS spectroscopy is applied to study orientation structures of polydimethylsilane (PDMS) films deposited on heteroatom-doped graphite substrates prepared by ion beam doping. The Si ${it K}$-edge NEXAFS spectra of PDMS show opposite trends of polarization dependence for non irradiated and N$$_{2}$$$$^{+}$$-irradiated substrates, and show no polarization dependence for an Ar$$^{+}$$-irradiated substrate. Based on a theoretical interpretation of the NEXAFS spectra via first-principles calculations, we clarify that PDMS films have lying, standing, and random orientations on the non irradiated, N$$_{2}$$$$^{+}$$-irradiated, and Ar$$^{+}$$-irradiated substrates, respectively. Furthermore, photoemission electron microscopy indicates that the orientation of a PDMS film can be controlled with microstructures on the order of $$mu$$m by separating irradiated and non irradiated areas on the graphite surface. These results suggest that surface modification of graphite using ion beam doping is useful for micro-orientation control of organic thin films.

Journal Articles

Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

Baba, Yuji; Shimoyama, Iwao; Hirao, Norie*

Applied Surface Science, 384, p.511 - 516, 2016/10


 Times Cited Count:5 Percentile:28.22(Chemistry, Physical)

Chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by total reflection X-ray photoelectron spectroscopy (TR-XPS). For cesium, it was shown that ultra-trace amount of cesium down to about 100 pg/cm$$^{-2}$$ can be detected by TR-XPS. This amount corresponds to about 200 Bq of $$^{137}$$Cs (t$$_{1/2}$$ = 30.2y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.

Journal Articles

Corrigendum to "Real time observation of oxygen chemisorption states on Si(001)-2$$times$$1 during supersonic oxygen molecular beam irradiation"

Teraoka, Yuden; Yoshigoe, Akitaka

Applied Surface Science, 346, P. 580, 2015/08

 Times Cited Count:0 Percentile:1.75(Chemistry, Physical)

Journal Articles

Corrigendum to "Si 2p and O 1s photoemission from oxidized Si(001) surfaces depending on translational kinetic energy of incident O$$_{2}$$ molecules"

Teraoka, Yuden; Yoshigoe, Akitaka

Applied Surface Science, 343, P. 212, 2015/07

 Times Cited Count:0 Percentile:1.75(Chemistry, Physical)

Journal Articles

Corrigendum to "Coexistence of passive and active oxidation for O$$_{2}$$/Si(001) system observed by SiO mass spectrometry and synchrotron radiation photoemission spectroscopy"

Teraoka, Yuden; Moritani, Kosuke*; Yoshigoe, Akitaka

Applied Surface Science, 343, P. 213, 2015/07

 Times Cited Count:0 Percentile:1.75(Chemistry, Physical)

Journal Articles

Corrigendum to "Commissioning of surface chemistry end-station in BL23SU of SPring-8"

Teraoka, Yuden; Yoshigoe, Akitaka

Applied Surface Science, 339, P. 158, 2015/06

Journal Articles

Effect of water vapor and hydrogen treatments on the surface structure of Ni$$_{3}$$Al foil

Xu, Y.*; Ma, Y.*; Sakurai, Junya*; Teraoka, Yuden; Yoshigoe, Akitaka; Demura, Masahiko*; Hirano, Toshiyuki*

Applied Surface Science, 315, p.475 - 480, 2014/10

 Times Cited Count:7 Percentile:33.87(Chemistry, Physical)

Journal Articles

Temperature dependence of Cu$$_{2}$$O formation on Cu$$_{3}$$Au(110) surface with energetic O$$_{2}$$ molecular beams

Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*

Applied Surface Science, 287, p.282 - 286, 2013/12

 Times Cited Count:6 Percentile:30.83(Chemistry, Physical)

Journal Articles

Oxidation of TiAl surface with hyperthermal oxygen molecular beams

Hashinokuchi, Michihiro*; Tode, Mayumi*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*

Applied Surface Science, 276, p.276 - 283, 2013/07

 Times Cited Count:4 Percentile:21.57(Chemistry, Physical)

Journal Articles

Well-ordered arranging of Ag nanoparticles in SiO$$_{2}$$/Si by ion implantation

Takahiro, Katsumi*; Ninakuchi, Yuki*; Kawaguchi, Kazuhiro; Isshiki, Toshiyuki*; Nishio, Koji*; Sasase, Masato*; Yamamoto, Shunya; Nishiyama, Fumitaka*

Applied Surface Science, 258(19), p.7322 - 7326, 2012/07

 Times Cited Count:2 Percentile:10.47(Chemistry, Physical)

A nanometer-sized metallic particle embedded in a transparent dielectric exhibits a nonlinear susceptibility, and going to be applied to nonlinear optical devices. In the present study, well-ordered arrangements of Ag nanoparticles have been found for Ag-implanted SiO$$_{2}$$. Thermally grown SiO$$_{2}$$ on Si were implanted with 350 keV-Ag ions to fluences of 0.37-1.2 $$times$$ 10$$^{17}$$ ions/cm$$^{2}$$. Cross-sectional transmission electron microscopy and scanning transmission electron microscopy reveal the presence of a two-dimensional array of Ag nanoparticles of 25-40 nm in diameter located at a depth of $$sim$$130 nm, together with the self-organization of tiny Ag nanoparticles aligned along the SiO$$_{2}$$/Si interface. X-ray photoelectron spectroscopy and X-ray diffraction confirm the stability of these Ag nanoparticles embedded in the SiO$$_{2}$$/Si is found to be stable against oxidation and sulfidation when stored in ambient conditions for more than one and a half year.

Journal Articles

Anchoring of alkyl chain molecules on oxide surface using silicon alkoxide

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Yaita, Tsuyoshi

Applied Surface Science, 258(6), p.2034 - 2037, 2012/01

 Times Cited Count:4 Percentile:20.56(Chemistry, Physical)

In order to apply the organic thin films to electric and optical devices, the immobilization of organic molecules on inorganic substrate is essential. Considering optical devices, it is important to immobilize organic molecules on oxide surfaces, because many of oxides have insulating and transparent properties. In this study, we have investigated the chemical states of the interface between organic molecules with silicon alkoxide and sapphire surfaces by X-ray photoelectron spectroscopy and near edge absorption fine structure (NEXAFS). Octadecyl-triethoxy-silane (ODTS) molecules which are terminated by silicon alkoxide were adsorbed on sapphire surfaces. On the basis of the Si 1s XPS spectra for monolayer, it is supposed that the chemical bond between silicon alkoxide and the surface is formed. For Si K-edge NEXAFS spectra, the polarization dependence was observed, which suggests that the Si-O bond in ODTS was located perpendicular to the surface.

Journal Articles

Study on selective adsorption of deuterium on boron nitride using photon-stimulated ion-desorption

Koswattage, K.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nakagawa, Kazumichi*

Applied Surface Science, 258(4), p.1561 - 1564, 2011/12

 Times Cited Count:6 Percentile:30.2(Chemistry, Physical)

Adsorption behavior of atomic deuterium on a hexagonal boron nitride (h-BN) thin film is studied by photon-stimulated ion desorption (PSID) of D$$^{+}$$ and near edge X-ray absorption fine structure (NEXAFS) at the B and N K-edges. After the adsorption of atomic deuterium, D$$^{+}$$ desorption yield $$eta$$(h$$nu$$) shows clear enhancement at the B K-edge and almost no enhancement at the N K-edge. NEXAFS spectra show a large change in the B K-edge and a small change in the N K-edge after the adsorption. We propose selective adsorption of atomic deuterium on the h-BN thin film based on the experimental results, and mention the effectiveness of applying the PSID method with X-ray to study hydrogen storage materials.

Journal Articles

Microscopic observation of lateral diffusion at Si-SiO$$_{2}$$ interface by photoelectron emission microscopy using synchrotron radiation

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori*

Applied Surface Science, 258(3), p.987 - 990, 2011/11

 Times Cited Count:3 Percentile:16.94(Chemistry, Physical)

The lateral surface diffusion at Si-SiO$$_{2}$$ interface has been observed at nanometer scale using photoelectron emission microscopy (PEEM) combined with synchrotron soft X-ray excitation. The samples investigated were Si-SiO$$_{x}$$ micro-patterns prepared by O$$_{2}$$$$^{+}$$ ion implantation in Si(0 0 1) wafer using a mask. The lateral spacial resolution of the PEEM system was about 41 nm. The brightness of each spot in the PEEM images changed depending on the photon energy around the Si ${it K}$-edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurs at lower temperature than that reported for the longitudinal diffusion at the Si-SiO$$_{2}$$ interface. It was also found that no intermediate valence states such as SiO (Si$$^{2+}$$) exist at the Si-SiO$$_{2}$$ interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).

Journal Articles

Optical emission spectroscopy by Ar$$^{3+}$$ ion sputtering of Ti surface under O$$_2$$ environment

Motohashi, Kenji*; Saito, Yuichi; Kitazawa, Sin-iti

Applied Surface Science, 257(13), p.5789 - 5792, 2011/04

 Times Cited Count:4 Percentile:21.66(Chemistry, Physical)

Journal Articles

Oxidation of TiNi surface with hyperthermal oxygen molecular beams

Okada, Michio*; Sowa, Makoto*; Kasai, Toshio*; Teraoka, Yuden

Applied Surface Science, 257(9), p.4257 - 4263, 2011/02

 Times Cited Count:11 Percentile:45.96(Chemistry, Physical)

Journal Articles

Dehydrogenation catalyst for optical organic-hydride detection

Yoshimura, Kimio; Hakoda, Teruyuki; Yamamoto, Shunya; Yoshikawa, Masahito

Applied Surface Science, 257(9), p.4428 - 4431, 2011/02

 Times Cited Count:5 Percentile:26.24(Chemistry, Physical)

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