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.

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

https://doi.org/10.1016/j.apsusc.2019.02.180

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. 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.

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

https://doi.org/10.1016/j.apsusc.2017.01.297

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 -edge NEXAFS spectra of PDMS show opposite trends of polarization dependence for non irradiated and N-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-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 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.

Corrigendum to "Real time observation of oxygen chemisorption states on Si(001)-21 during supersonic oxygen molecular beam irradiation"

Teraoka, Yuden; Yoshigoe, Akitaka

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

https://doi.org/10.1016/j.apsusc.2015.02.145

Corrigendum to "Coexistence of passive and active oxidation for O/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

https://doi.org/10.1016/j.apsusc.2015.02.147

Effect of water vapor and hydrogen treatments on the surface structure of NiAl foil

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

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

https://doi.org/10.1016/j.apsusc.2014.02.144

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

https://doi.org/10.1016/j.apsusc.2013.03.082

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

https://doi.org/10.1016/j.apsusc.2011.04.111

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.

Microscopic observation of lateral diffusion at Si-SiO 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

https://doi.org/10.1016/j.apsusc.2011.04.047

The lateral surface diffusion at Si-SiO 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 micro-patterns prepared by O 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 -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 interface. It was also found that no intermediate valence states such as SiO (Si) exist at the Si-SiO interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).

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

https://doi.org/10.1016/j.apsusc.2010.12.033