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species at SiO/Si interfaces in Si dry oxidation; Comparison between p-Si(001) and n-Si(001) surfacesTsuda, Yasutaka; Yoshigoe, Akitaka; Ogawa, Shuichi*; Sakamoto, Tetsuya*; Yamamoto, Yoshiki*; Yamamoto, Yukio*; Takakuwa, Yuji*
Journal of Chemical Physics, 157(23), p.234705_1 - 234705_21, 2022/12
Times Cited Count：1 Percentile：9.30(Chemistry, Physical)
molecule at SiO/Si(001) interface during Si dry oxidationTsuda, Yasutaka; Yoshigoe, Akitaka; Ogawa, Shuichi*; Sakamoto, Tetsuya*; Takakuwa, Yuji*
e-Journal of Surface Science and Nanotechnology (Internet), 21(1), p.30 - 39, 2022/11
observation of surface reactions; Present status and future prospects"Yoshigoe, Akitaka; Ogawa, Shuichi*; Takakuwa, Yuji*
Hoshako, 35(3), P. 157, 2022/05
Ambient Pressure-XPS [AP-XPS] has been in operation at synchrotron radiation facilities around the world since around 2000 to study gas-surface reactions. Furthermore, it is also applied to observe liquid and solid-liquid interfaces. Development and utilization research is underway as a tool to take the true picture of surface phenomena. A special issue on AP-XPS for the Journal of the Japanese Society for Synchrotron Radiation Research was designed and its purpose is explained.
observation of surface reactions under the gas atmosphere; History, applications, issues, and future prospectTakakuwa, Yuji*; Ogawa, Shuichi*; Yoshigoe, Akitaka
Hoshako, 35(3), p.158 - 171, 2022/05
Ambient pressure X-ray photoelectron spectroscopy for in situ observation of surface reactions using high-brightness synchrotron radiation shows a rapid progress in the number of endstations since about 2005 and is applied to various practical research field for clarifying reactions at solid/gas interfaces of e.g. catalyst, solid/liquid interfaces of e.g. fuel cell, and gas/liquid interfaces of e.g. ion liquid. In this review, a history of the development of APXPS, real-time observation of the surface reactions for Si chemical vapor deposition and Si dry oxidation, issues of APXPS, and future prospects are described.
Ogawa, Shuichi*; Taga, Ryo*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Journal of Vacuum Science and Technology A, 39(4), p.043207_1 - 043207_9, 2021/07
Times Cited Count：1 Percentile：5.74(Materials Science, Coatings & Films)Nickel (Ni) is used as a catalyst for nitric oxide decomposition and ammonia production but it is easily oxidized and deactivated. Clarification of the reduction process of oxidized Ni is essential to promote more efficient use of Ni catalysts. In this study, the reduction processes were investigated by in situ time-resolved photoelectron spectroscopy. We propose a two-step reduction reaction model. The rate-limiting process for the first step is surface precipitation of O atoms and that of the second step is dissociation of H molecules.
Ogawa, Shuichi*; Zhang, B.*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Vacuum and Surface Science, 64(5), p.218 - 223, 2021/05
The oxidation reaction kinetics on Ti(0001) and Ni(111) surfaces were observed by real-time photoelectron spectroscopy using synchrotron radiation to measure the oxidation state and oxide thickness. After the Ti(0001) surface was wholly covered by TiO with a thickness of 1.2 nm, the rapid growth of n-type TiO proceeded through the diffusion of Ti
ions to the TiO surface at 400
C. A saturation of oxygen uptake on the TiO surface indicates that the O sticking coefficient on the TiO surface is negligibly small and the segregation of Ti to the TiO surface is a trigger to initiate the TiO growth. On the Ni(111) surface at 350C, a thermally stable NiO
proceeded preferentially and then the growth of p-type NiO was initiated. The time evolution of NiO thickness was represented by a logarithmic growth model, where the NiO growth is governed by the electron tunneling to the NiO surface.
Ogawa, Shuichi*; Yamaguchi, Hisato*; Holby, E. F.*; Yamada, Takatoshi*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Journal of Physical Chemistry Letters (Internet), 11(21), p.9159 - 9164, 2020/11
Times Cited Count：3 Percentile：15.53(Chemistry, Physical)Atomically thin layers of graphene have been proposed to protect surfaces through the direct blocking of corrosion reactants such as oxygen with low added weight. The long term efficacy of such an approach, however, is unclear due to the long-term desired protection of decades and the presence of defects in as-synthesized materials. Here, we demonstrate catalytic permeation of oxygen molecules through previously-described impermeable graphene by imparting sub-eV kinetic energy to molecules. These molecules represent a small fraction of a thermal distribution thus this exposure serves as an accelerated stress test for understanding decades-long exposures. The permeation rate of the energized molecules increased 2 orders of magnitude compared to their non-energized counterpart. Graphene maintained its relative impermeability to non-energized oxygen molecules even after the permeation of energized molecules indicating that the process is non-destructive and a fundamental property of the exposed material.
Ogawa, Shuichi*; Yoshigoe, Akitaka; Tang, J.*; Sekihata, Yuki*; Takakuwa, Yuji*
Japanese Journal of Applied Physics, 59(SM), p.SM0801_1 - SM0801_42, 2020/07
Times Cited Count：6 Percentile：33.94(Physics, Applied)In this paper, we review the study of the unified Si oxidation reaction model mediated by point defect generation, in which O dissociative adsorption occurs at dangling bonds of point defects (emitted Si atoms and vacancies) at the SiO/Si interface, and the point defect generation rate is given by a combination of oxidation-induced strain, thermal strain due to the difference in thermal expansion coefficient between Si and SiO, thermal excitation of Si emission rate, and heat of adsorption.
Ogawa, Shuichi*; Yoshigoe, Akitaka; Takakuwa, Yuji*
Vacuum and Surface Science, 62(6), p.350 - 355, 2019/06
Thermal oxidation of Si substrate is an indispensable process for the Si device fabrication. However, the influence of oxidation induced strain cannot be ignored for thin films. Synchrotron radiation real-time photoelectron spectroscopy was used as a method to measure simultaneously oxidation induced strain and oxidation rate. It was found that the acceleration of interfacial oxidation induced by thermal strain was observed for the rapid thermal oxidation. The results can be explained by the model in which point defects caused by strain become reaction sites at the SiO/Si interface.
1 surface; In situ synchrotron radiation photoemission studyYoshigoe, Akitaka; Yamada, Yoichi*; Taga, Ryo*; Ogawa, Shuichi*; Takakuwa, Yuji*
Japanese Journal of Applied Physics, 55(10), p.100307_1 - 100307_4, 2016/09
Times Cited Count：5 Percentile：23.64(Physics, Applied)Synchrotron radiation photoelectron spectroscopy during the oxidation of the Si(100)21 surface at room temperature revealed the existence of the molecularly adsorbed oxygen, which was considered to be absent. The O 1s spectra was found to be similar to that of the oxidation of Si(111)77 surfaces. Also the molecular oxygen was appeared after the initial surface oxides, indicating that this was not a precursor for dissociation oxygen adsorption onto the clean surface. We have proposed presumable structural models for atomic configurations, where the molecular oxygen was resided on the oxidized silicon with two oxygen atoms at the backbonds.
/Si(001) interfacial oxidation induced by thermal strain during rapid thermal oxidationOgawa, Shuichi*; Tang, J.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Takakuwa, Yuji*
Journal of Chemical Physics, 145(11), p.114701_1 - 114701_7, 2016/09
Times Cited Count：5 Percentile：18.17(Chemistry, Physical)Enhancement of SiO/Si(001) interfacial oxidation induced by thermal strain during rapid thermal oxidation was revealed by real time photoelectron spectroscopy using high intensity and high energy-resolution synchrotron radiation. This experimental result indicates the usefulness of the unified Si oxidation reaction model mediated by point defect generation.
Yamaguchi, Hisato*; Ogawa, Shuichi*; Watanabe, Daiki*; Hozumi, Hideaki*; Gao, Y.*; Eda, Goki*; Mattevi, C.*; Fujita, Takeshi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; et al.
Physica Status Solidi (A), 213(9), p.2380 - 2386, 2016/09
Times Cited Count：14 Percentile：50.63(Materials Science, Multidisciplinary)We report valence-band electronic structure evolution of graphene oxide (GO) upon its thermal reduction. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored using real-time ultraviolet photoelectron spectroscopy. We observed a drastic increase in the density of states around the Fermi level upon thermal annealing at 
600C. The result indicates that while there is an apparent bandgap for GO prior to a thermal reduction, the gap closes after an annealing around that temperature. This trend of bandgap closure was correlated with the electrical, chemical, and structural properties to determine a set of GO material properties that is optimal for optoelectronics. The results revealed that annealing at a temperature of 500C leads to the desired properties, demonstrated by a uniform and an order of magnitude enhanced photocurrent map of an individual GO sheet compared to an as-synthesized counterpart.
7 surfaces studied by real-time photoelectron spectroscopyTang, J.*; Nishimoto, Kiwamu*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Watanabe, Daiki*; Teraoka, Yuden; Takakuwa, Yuji*
Surface and Interface Analysis, 46(12-13), p.1147 - 1150, 2014/12
Times Cited Count：1 Percentile：1.60(Chemistry, Physical)O
substratesOgawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*
Japanese Journal of Applied Physics, 52(11), p.110122_1 - 110122_8, 2013/11
Times Cited Count：20 Percentile：62.30(Physics, Applied)/Si(001) interfaces during thermal oxidationOgawa, Shuichi*; Tang, J.*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*
Japanese Journal of Applied Physics, 52(11), p.110128_1 - 110128_7, 2013/11
Times Cited Count：13 Percentile：45.86(Physics, Applied)Tang, J.*; Nishimoto, Kiwamu*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Watanabe, Daiki*; Teraoka, Yuden; Takakuwa, Yuji*
e-Journal of Surface Science and Nanotechnology (Internet), 11, p.116 - 121, 2013/11
pressure dependence of the initial oxide growth kinetics on Si(111) surfaces; Photoelectron spectroscopy observation and molecular orbital calculation of oxidation statesTang, J.*; Nishimoto, Kiwamu*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Watanabe, Daiki*; Teraoka, Yuden; Takakuwa, Yuji*
Dai-18-Kai Getosutakku KenkyuKai Yokoshu, p.191 - 194, 2013/01
Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*
Japanese Journal of Applied Physics, 51(11), p.11PF02_1 - 11PF02_7, 2012/11
Times Cited Count：30 Percentile：72.94(Physics, Applied)Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Watanabe, Daiki*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*
Hyomen Kagaku, 33(8), p.449 - 454, 2012/08
Graphene-on-insulator structures are required for fabrication of the graphene transistor. Diamond has been attracted as the substrate for graphene growth because it has a larger band gap and break down voltage compared with SiC. The detail of graphitization on a diamond surface has not been clarified yet because the nondestructive evaluation for graphene-on-diamond (GOD) structure was hard. In this study, we have developed an evaluation method of GOD based on the photoemission spectroscopy using synchrotron radiation focusing the shift of photoelectron spectra due to band bending. We can clearly determine the graphitization temperature on the diamond C(111) surface as approximately 1120 K, which is lower than that on an SiC substrate. It is also confirmed from C 1s photoelectron spectra, there is the buffer layer at the interface between the grapheme layer and the diamond substrate.
Ge alloy layer studied by real-time photoelectron spectroscopyOgawa, Shuichi*; Hozumi, Hideaki*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Kaga, Toshiteru*; Teraoka, Yuden; Takakuwa, Yuji*
Oyo Butsuri Gakkai Hakumaku, Hyomen Butsuri Bunkakai, Shirikon Tekunoroji Bunkakai Kyosai Tokubetsu Kenkyukai Kenkyu Hokoku, p.67 - 70, 2011/01
The oxidation-enhanced Ge atoms condensation kinetics on an SiGe alloy layer has been investigated by the real-time photoemission spectroscopy using the synchrotron radiation. The SiGe alloy layer was formed with a thermal evaporation method on a p-type Si(001) surface, and this alloy layer was oxidized at Langmuir-type adsorption. During oxidation at 773 KC, it is found that the Ge atoms are not oxidized, only SiO film is formed on the SiGe alloy layer. Furthermore, the desorption of GeO molecules does not occur during the oxidation of alloy layer. On the other hand, not only Si atoms but also Ge atoms are oxidized at room temperature. This difference can be explained using the unified oxidation model mediated by the point defect generation, namely it is suggested that a lot of vacancies are generated during oxidation of the SiGe alloy layer at 773K and Ge atoms diffuse through these vacancies.
