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Makino, Takamasa*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Dio, W. A.*; Okada, Michio*
Applied Surface Science, 642, p.158568_1 - 158568_6, 2024/01
Times Cited Count:0 Percentile:0.01(Chemistry, Physical)Tsuda, Yasutaka; Gueriba, J. S.*; Ueta, Hirokazu*; Dio, W. A.*; Kurahashi, Mitsunori*; Okada, Michio*
JACS Au (Internet), 2(8), p.1839 - 1847, 2022/08
Hayashida, Koki*; Tsuda, Yasutaka; Yamada, Takashi*; Yoshigoe, Akitaka; Okada, Michio*
ACS Omega (Internet), 6(40), p.26814 - 26820, 2021/10
Times Cited Count:7 Percentile:47.89(Chemistry, Multidisciplinary)We report the X-ray photoemission spectroscopy (XPS) characterization of the bulk CuO(111) surface and 8-type and 29-type oxide structures on Cu(111) prepared by using 0.5 eV O supersonic molecular beam (SSMB) source. We propose a new structural model for the 8-type oxide structure and also confirmed the previously proposed model for the [29] oxide structure on Cu(111), based on the O1s XPS spectra. The detection-angle dependence of the O 1s spectra supports that the nanopyramidal model is more preferable for the (X)R30 CuO(111). We also report the electronic excitations which O1s electrons suffer.
Tsuda, Yasutaka; Gueriba, J. S.*; Makino, Takamasa*; Dio, W. A.*; Yoshigoe, Akitaka; Okada, Michio*
Scientific Reports (Internet), 11, p.3906_1 - 3906_8, 2021/02
Times Cited Count:3 Percentile:14.79(Multidisciplinary Sciences)Okada, Michio*; Tsuda, Yasutaka*; Yoshigoe, Akitaka; Dio, W. A.*
Do To Dogokin, 56(1), p.232 - 236, 2017/00
We reported the our studies on the surface temperature (Ts) dependence of oxidation on the CuAu(111) surface by a supersonic O molecular beam, using synchrotron radiation X-ray photoemission spectroscopy. Clean surface shows strong Au segregation to the top layer, i.e., Au surface enrichment of the clean surface. Complete Cu segregation to the surface occurs at 0.5 ML O surface coverage. The Au-rich second and third layers of the oxidized surface demonstrate the protective layer formation against oxidation deeper into the bulk. We found that CuO formation occurs. At Ts = 300K, the CuO growth is not so effective. The surface oxidation is less effective on CuAu(111) than on Cu(111). At Ts = 400K, the protection by the Au-rich layer against oxidation into bulk is effective. At Ts = 500K, the Au protective layer is broken due to effective Au diffusion and thus CuO grows deeper into bulk.
Okada, Michio*; Tsuda, Yasutaka*; Oka, Kohei*; Kojima, Kazuki*; Dio, W. A.*; Yoshigoe, Akitaka; Kasai, Hideaki*
Scientific Reports (Internet), 6, p.31101_1 - 31101_8, 2016/08
Times Cited Count:28 Percentile:73.15(Multidisciplinary Sciences)We report results of our experimental and theoretical studies on the oxidation of Cu-Au alloy surfaces, viz., CuAu(111), CuAu(111), and AuCu(111), using hyperthermal O molecular beam (HOMB). We observed strong Au segregation to the top layer of the corresponding clean (111) surfaces. This forms a protective layer that hinders further oxidation into the bulk. The higher the concentration of Au in the protective layer formed, the higher the protective efficacy. As a result, of the three Cu-Au surfaces studied, AuCu(111) is the most stable against dissociative adsorption of O, even with HOMB. We also found that this protective property breaks down for oxidations occurring at temperatures above 300 K.
Tsuda, Yasutaka*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*
Materials Research Express (Internet), 3(3), p.035014_1 - 035014_8, 2016/03
Times Cited Count:5 Percentile:18.55(Materials Science, Multidisciplinary)We report a study on the surface-temperature () dependence of oxidation process at CuAu(111) by using a hyperthermal oxygen molecular beam and synchrotron-radiation X-ray photoemission spectroscopy. The O-1s spectra and the corresponding O-uptake curves demonstrate that CuO domains grow effectively at high of 400 and 500 K. The simple analysis of the O distribution suggests that the temperature-induced atomic diffusion causes the CuO domains growing thicker at 500 K. The oxidation of CuAu(111) is less efficient at = 300-500 K than that of Cu(111), demonstrating that the protective nature of CuAu against oxidation, in comparison to Cu, remains even at high .
Oka, Kohei*; Tsuda, Yasutaka*; Makino, Takamasa*; Okada, Michio*; Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Hideaki*
Physical Chemistry Chemical Physics, 16(36), p.19702 - 19711, 2014/08
Times Cited Count:11 Percentile:39.91(Chemistry, Physical)Tsuda, Yasutaka*; Oka, Kohei*; Makino, Takamasa*; Okada, Michio*; Dio, W. A.*; Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Hideaki*
Physical Chemistry Chemical Physics, 16(8), p.3815 - 3822, 2014/02
Times Cited Count:14 Percentile:48.54(Chemistry, Physical)Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*
Applied Surface Science, 287, p.282 - 286, 2013/12
Times Cited Count:6 Percentile:29.2(Chemistry, Physical)Hashinokuchi, Michihiro*; Tode, Mayumi*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*
Applied Surface Science, 276, p.276 - 283, 2013/07
Times Cited Count:4 Percentile:20.37(Chemistry, Physical)Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*
Journal of Physics; Condensed Matter, 24(39), p.395007_1 - 395007_8, 2012/10
Times Cited Count:5 Percentile:23.8(Physics, Condensed Matter)Okada, Michio*; Vattuone, L.*; Rocca, M.*; Teraoka, Yuden
Journal of Chemical Physics, 136(9), p.094704_1 - 094704_8, 2012/03
Times Cited Count:8 Percentile:27.83(Chemistry, Physical)Sowa, Makoto*; Yamazaki, Daichi*; Okada, Michio*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Toshio*
Electrical Engineering in Japan, 175(4), p.43 - 47, 2011/06
Times Cited Count:2 Percentile:18.44(Engineering, Electrical & Electronic)Yamazaki, Daichi*; Sowa, Makoto*; Okada, Michio*; Teraoka, Yuden; Kasai, Toshio*
Journal of the Vacuum Society of Japan, 54(5), p.307 - 312, 2011/05
Okada, Michio*; Sowa, Makoto*; Kasai, Toshio*; Teraoka, Yuden
Applied Surface Science, 257(9), p.4257 - 4263, 2011/02
Times Cited Count:11 Percentile:44.43(Chemistry, Physical)Hashinokuchi, Michihiro*; Sumimoto, Yuichi*; Tode, Mayumi; Harries, J.; Okada, Michio*; Teraoka, Yuden; Kasai, Toshio*
Denki Gakkai Rombunshi, C, 130(10), p.1723 - 1729, 2010/10
The oxidation processes on a TiAl surface induced by a hyperthermal O molecular beam (HOMB) with a translational energy of 2.2 eV was studied by X-ray photoemission spectroscopy in conjunction with synchrotron radiation. At a surface temperature of 300 K, the simultaneous growth of Al and Ti oxides accompanied with the segregation of AlO near the surface was observed. The efficiency of oxidation for the HOMB incidence was smaller than that for O backfilling (25 meV). Furthermore, the chemical compositions of oxide species (AlO, TiO, TiO) on the TiAl surface were independent of the translational energy of incident O molecule. The present results suggest that the oxidation on TiAl surface proceeds via precursor molecular states.
Okada, Michio*; Teraoka, Yuden
Applied Surface Science, 256(18), p.5676 - 5680, 2010/07
Times Cited Count:8 Percentile:37.32(Chemistry, Physical)Oxidation of CuAu(110) using a hyperthermal O molecular beam (HOMB) was investigated by synchrotron X-ray photoemission spectroscopy. From the incident energy dependence of the O-uptake curve, the precursor-mediated dissociative adsorption occurs, where the trapped O molecule can migrate and dissociate at the lower activation-barrier sites. Dissociative adsorption of O on CuAu(110) is as effective at the thermal O exposure as on Cu(110). On the other hand, at the incident energies of HOMB where the direct dissociative adsorption is dominant, the dissociative adsorption of O takes place with a higher activation barrier and less reactivity due to Au alloying comparing to the HOMB oxidation of Cu(110). The dissociative adsorption progresses with the Cu segregation on CuAu(110) similarly as on CuAu(100). The growth of CuO for 2 eV HOMB suggests that the diffusion of Cu also contribute to the oxidation.
Okada, Michio*; Moritani, Kosuke*; Vattuone, L.*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*
Metal Oxide Nanostructures and Their Applications, 1, p.205 - 237, 2010/03
The use of hyperthermal O molecular beams may improve the quality of thin film growth, for example, for organic films, and allow the production of oxide layers at lower crystal temperatures, avoiding contamination problems and reducing film defects. Collision-induced absorption and local heating of the substrate were shown to be indeed effective in inducing oxide nucleation, opening up new possibilities for the production of nanostructured metal oxides. Herein we offer an overview on recent detailed studies of oxygen adsorption and of the initial stages of CuO and CuO formation on low Miller index and vicinal Cu surfaces. We introduce the hyperthermal molecular beam technique and give some details on the experimental apparatuses. We discuss the available data for Cu(100), Cu(410) and Cu(110) and Cu(111), respectively.
Moritani, Kosuke*; Okada, Michio*; Teraoka, Yuden; Yoshigoe, Akitaka; Kasai, Toshio*
Journal of Physical Chemistry A, 113(52), p.15217 - 15222, 2009/10
Times Cited Count:11 Percentile:35.39(Chemistry, Physical)Oxygen adsorption and subsequent oxide formation on Cu(110) using a hyperthermal oxygen molecular beam (HOMB) has been investigated using SR-XPS. The O-uptake curves, which were determined from the evolution of O-1s peaks, indicate that simple Langmuir type kinetics can describe dissociative adsorption of O with an incident energy (Ei) below 0.5eV under oxygen coverage of 0.5 ML. The reaction order dependence on Ei implies two competing dissociation mechanisms, trapping-mediated and directly-activated adsorption. Oxidation at oxygen coverage larger than 0.5 ML proceeds rather effectively using highly energetic HOMB at Ei larger than 1.0 eV. The surface CuO formed with highly-energetic HOMB incidence decomposes with desorbing subsurface oxygen even at room temperature. This indicates that HOMB can induce a meta stable surface structure that cannot be produced in the thermal equilibrium process.