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Journal Articles

CH$$_3$$Cl dissociation, CH$$_3$$ abstraction, and Cl adsorption from the dissociative scattering of supersonic CH$$_3$$Cl on Cu(111) and Cu(410)

Makino, Takamasa*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Di$~n$o, W. A.*; Okada, Michio*

Applied Surface Science, 642, p.158568_1 - 158568_6, 2024/01

Journal Articles

Probing copper and copper-gold alloy surfaces with space-quantized oxygen molecular beam

Tsuda, Yasutaka; Gueriba, J. S.*; Ueta, Hirokazu*; Di$~n$o, W. A.*; Kurahashi, Mitsunori*; Okada, Michio*

JACS Au (Internet), 2(8), p.1839 - 1847, 2022/08

Journal Articles

Revisit of XPS studies of supersonic O$$_{2}$$ molecular adsorption on Cu(111); Copper oxides

Hayashida, Koki*; Tsuda, Yasutaka; Yamada, Takashi*; Yoshigoe, Akitaka; Okada, Michio*

ACS Omega (Internet), 6(40), p.26814 - 26820, 2021/10

 Times Cited Count:3 Percentile:33.58(Chemistry, Multidisciplinary)

We report the X-ray photoemission spectroscopy (XPS) characterization of the bulk Cu$$_{2}$$O(111) surface and 8-type and 29-type oxide structures on Cu(111) prepared by using 0.5 eV O$$_{2}$$ 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 ($$sqrt{3}$$X$$sqrt{3}$$)R30$$^{circ}$$ Cu$$_{2}$$O(111). We also report the electronic excitations which O1s electrons suffer.

Journal Articles

Interface atom mobility and charge transfer effects on CuO and Cu$$_{2}$$O formation on Cu$$_{3}$$Pd(111) and Cu$$_{3}$$Pt(111)

Tsuda, Yasutaka; Gueriba, J. S.*; Makino, Takamasa*; Di$~n$o, W. A.*; Yoshigoe, Akitaka; Okada, Michio*

Scientific Reports (Internet), 11, p.3906_1 - 3906_8, 2021/02

 Times Cited Count:2 Percentile:10.82(Multidisciplinary Sciences)

Journal Articles

Oxidation processes of copper-gold alloy surface induced by supersonic oxygen molecular beam

Okada, Michio*; Tsuda, Yasutaka*; Yoshigoe, Akitaka; Di$~n$o, 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 Cu$$_{3}$$Au(111) surface by a supersonic O$$_{2}$$ 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 Cu$$_{2}$$O formation occurs. At Ts = 300K, the Cu$$_{2}$$O growth is not so effective. The surface oxidation is less effective on Cu$$_{3}$$Au(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 Cu$$_{2}$$O grows deeper into bulk.

Journal Articles

Experimental and theoretical studies on oxidation of Cu-Au alloy surfaces; Effect of bulk Au concentration

Okada, Michio*; Tsuda, Yasutaka*; Oka, Kohei*; Kojima, Kazuki*; Di$~n$o, W. A.*; Yoshigoe, Akitaka; Kasai, Hideaki*

Scientific Reports (Internet), 6, p.31101_1 - 31101_8, 2016/08

 Times Cited Count:24 Percentile:71.25(Multidisciplinary Sciences)

We report results of our experimental and theoretical studies on the oxidation of Cu-Au alloy surfaces, viz., Cu$$_{3}$$Au(111), CuAu(111), and Au$$_{3}$$Cu(111), using hyperthermal O$$_{2}$$ 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, Au$$_{3}$$Cu(111) is the most stable against dissociative adsorption of O$$_{2}$$, even with HOMB. We also found that this protective property breaks down for oxidations occurring at temperatures above 300 K.

Journal Articles

Surface temperature dependence of oxidation of Cu$$_{3}$$Au(111) by an energetic oxygen molecule

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:19.11(Materials Science, Multidisciplinary)

We report a study on the surface-temperature ($$T_{s}$$) dependence of oxidation process at Cu$$_{3}$$Au(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 Cu$$_{2}$$O domains grow effectively at high $$T_{s}$$ of 400 and 500 K. The simple analysis of the O distribution suggests that the temperature-induced atomic diffusion causes the Cu$$_{2}$$O domains growing thicker at 500 K. The oxidation of Cu$$_{3}$$Au(111) is less efficient at $$T_{s}$$ = 300-500 K than that of Cu(111), demonstrating that the protective nature of Cu$$_{3}$$Au against oxidation, in comparison to Cu, remains even at high $$T_{s}$$.

Journal Articles

The Effects of alloying and segregation for the reactivity and diffusion of oxygen on Cu$$_{3}$$Au(111)

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:40.89(Chemistry, Physical)

Journal Articles

Initial stages of Cu$$_{3}$$Au(111) oxidation; Oxygen induced Cu segregation and the protective Au layer profile

Tsuda, Yasutaka*; Oka, Kohei*; Makino, Takamasa*; Okada, Michio*; Di$~n$o, 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:49.47(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:29.65(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:20.75(Chemistry, Physical)

Journal Articles

The Temperature dependence of Cu$$_{2}$$O formation on a Cu(110) surface with an energetic O$$_{2}$$ molecular beam

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:24.18(Physics, Condensed Matter)

Journal Articles

The Effect of step geometry in copper oxidation by hyperthermal O$$_{2}$$ molecular beam; Cu(511) vs Cu(410)

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:28.36(Chemistry, Physical)

Journal Articles

Photoemission study on natural oxidation of Cu$$_{3}$$Au with synchrotron radiation

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:18.58(Engineering, Electrical & Electronic)

Journal Articles

Synchrotron X-ray photoemission study of NiTi surface oxidation with hyperthermal oxygen molecular beam

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

Journal of the Vacuum Society of Japan, 54(5), p.307 - 312, 2011/05

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:44.85(Chemistry, Physical)

Journal Articles

The Study of oxidation on TiAl surface with photoemission spectroscopy in conjunction with synchrotron radiation

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$$_{2}$$ 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 Al$$_{2}$$O$$_{3}$$ near the surface was observed. The efficiency of oxidation for the HOMB incidence was smaller than that for O$$_{2}$$ backfilling (25 meV). Furthermore, the chemical compositions of oxide species (Al$$_{2}$$O$$_{3}$$, Ti$$_{2}$$O$$_{3}$$, TiO$$_{2}$$) on the TiAl surface were independent of the translational energy of incident O$$_{2}$$ molecule. The present results suggest that the oxidation on TiAl surface proceeds via precursor molecular states.

Journal Articles

Active oxidation of Cu$$_{3}$$Au(110) using hyperthermal O$$_{2}$$ molecular beam

Okada, Michio*; Teraoka, Yuden

Applied Surface Science, 256(18), p.5676 - 5680, 2010/07

 Times Cited Count:8 Percentile:37.63(Chemistry, Physical)

Oxidation of Cu$$_{3}$$Au(110) using a hyperthermal O$$_{2}$$ 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$$_{2}$$ molecule can migrate and dissociate at the lower activation-barrier sites. Dissociative adsorption of O$$_{2}$$ on Cu$$_{3}$$Au(110) is as effective at the thermal O$$_{2}$$ 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$$_{2}$$ 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 Cu$$_{3}$$Au(110) similarly as on Cu$$_{3}$$Au(100). The growth of Cu$$_{2}$$O for 2 eV HOMB suggests that the diffusion of Cu also contribute to the oxidation.

Journal Articles

Fabrication of Cu oxides on single crystal Cu surfaces using hyperthermal O$$_{2}$$ molecular beams

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$$_{2}$$ 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 Cu$$_{2}$$O 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.

Journal Articles

Kinetics of oxygen adsorption and initial oxidation on Cu(110) by hyperthermal oxygen molecular beams

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:35.77(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$$_{2}$$ 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 Cu$$_{2}$$O 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.

97 (Records 1-20 displayed on this page)