Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
molecular beamsOkada, 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.
O formation via hyperthermal O adsorption at Cu(410)Okada, Michio*; Vattuone, L.*; Gerbi, A.*; Savio, L.*; Rocca, M.*; Moritani, Kosuke*; Teraoka, Yuden; Kasai, Toshio*
Journal of Physical Chemistry C, 111(46), p.17340 - 17345, 2007/11
Times Cited Count：18 Percentile：50.9(Chemistry, Physical)We report a study on the oxidation process of Cu(410) using high-resolution electron energy loss spectroscopy and X-ray photoemission spectroscopy using synchrotron radiation. We demonstrate that a hyperthermal O molecular beam (HOMB) is an efficient tool to fabricate CuO thin film also at room temperature. The efficiency of the CuO formation in the initial stages depends on the angle of incidence of HOMB. Step roughening, acting as a source of mobile precursor Cu adatoms and opening channels for bulk diffusion of the O atoms, is a key feature in determining the CuO formation rate.
Okada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*
Journal of Physics; Condensed Matter, 19(30), p.305022_1 - 305022_7, 2007/08
Times Cited Count：8 Percentile：38.62(Physics, Condensed Matter)We studied the oxidation of Cu(410) for thermal O exposure and using High-resolution Electron Energy-loss Spectroscopy. CuO is identified by loss peaks at 19 meV and 79 meV. By monitoring the intensity of the latter, we find that CuO formation depends strongly on surface temperature and on O pressure and is kinetically limited by the impinging O flux. Thermally activated step roughening, leading to detachment of Cu adatoms from the step edge, acts as a source of mobile Cu atoms allowing for subsequent nucleation of CuO patches.
molecular beamOkada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*
Physical Review B, 75(23), p.233413_1 - 233413_4, 2007/06
Times Cited Count：34 Percentile：76.74(Materials Science, Multidisciplinary)We studied the oxidation of Cu(410) using X-ray photoemission spectroscopy performed with synchrotron radiation. We demonstrate that a hyperthermal O molecular beam is an efficient tool to fabricate Cu oxide thin films at room temperature (RT) and even lower temperatures. At RT, mainly CuO forms. At around 100 K, CuO nucleation also takes place; this is noteworthy, since this moiety is usually produced only at much higher 
and ambient pressure.
O formation on Cu(410) using a hyperthermal O molecular beamOkada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Gerbi, A.*; Savio, L.*; Yoshigoe, Akitaka; Teraoka, Yuden; Rocca, M.*; Kasai, Toshio*
no journal, ,
Herein we report the results of our detailed studies on the initial oxidation process, especially the CuO formation, on Cu(410). From the high-resolution electron energy-loss spectroscopy (HREELS), the CuO formation is verified at a high temperature for the thermal O exposure. However, from the X-ray photoemission spectroscopy (XPS) measurements in conjunction with synchrotron radiation (SR), the efficiency of CuO formation is quite low for the thermal O exposure. On the other hand, it was found on Cu(410) that hyperthermal O molecular beams (HOMB) at 2.2eV is an efficient tool for the fabrication of CuO even at room temperature or at lower temperatures. The O-1s and valence-band XPS spectra clearly demonstrate the characteristic features of CuO formation induced by HOMB. Furthermore, such CuO formation depends strongly on the azimuthal direction of the incident HOMB, impinging dominantly on a terrace or on a step.
O formation on Cu(410) using a hyperthermal O molecular beamOkada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Gerbi, A.*; Savio, L.*; Yoshigoe, Akitaka; Teraoka, Yuden; Rocca, M.*; Kasai, Toshio*
no journal, ,
It is important to make clear oxidation processes of Cu from an industrial view point because cupper oxides are candidates of high-Tc super conductor and solar cells. However, the details of the chemical reaction dynamics for the Cu oxidation processes have not been understood yet. We have already studied initial oxidation processes of Cu(100) and Cu(110) surfaces by using supersonic oxygen molecular beams. In this research, effects of surface defects for the surface oxidation are investigated by using the Cu(410) surface with large step density. It was found that oxidation rate of the Cu(410) surface was larger than Cu(100) surface, but, smaller than Cu(110) surface in the oxygen coverage range larger than 0.5 monolayer, from which formation of CuO was observed. The phenomenon can be understood from the fact that the (410) surface consists of (100) terraces and (110) steps.
molecular beamOkada, Michio*; Vattuone, L.*; Savio, L.*; Moritani, Kosuke*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*
no journal, ,
We report the detailed studies on the initial oxidation process of the CuO and CuO formation on stepped surfaces of Cu(410). From high-resolution electron energy-loss spectroscopy, CuO formation is verified at high temperature for thermal O exposure. However, from synchrotron radiation photoemission spectroscopy we found the efficiency of CuO formation to be quite low for thermal O exposure. On the contrary, hyperthermal oxygen molecular beam (HOMB) at 2.2 eV was efficient for the fabrication of CuO even at room temperature. The O-1s and valence-band XPS spectra clearly demonstrated the CuO formation induced by the HOMB. Furthermore, such CuO formation depended strongly on the azimuthal direction of the incident HOMB, impinging dominantly either on a terrace or on a step. At low temperature of around 100 K, we found the nucleation of a metastable CuO phase which evolved into stable CuO when the crystal was heated.
molecular beamOkada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Gerbi, A.*; Savio, L.*; Yoshigoe, Akitaka; Teraoka, Yuden; Rocca, M.*; Kasai, Toshio*
no journal, ,
Initial oxidation processes at Cu(100) and Cu(410) surfaces by hyperthermal oxygen molecular beams (HOMB) have been investigated. In order to make clear effects of surface temperature, oxidation behaviour of steps at the Cu(410) surface, which had a moderate oxidation rate, was studied by high energy-resolution X-ray photoemission spectroscopy at the BL23SU in the SPring-8. Consequently, formation of CuO was observed at room temperature by using HOMB of about 2 eV. And metastable CuO was formed at 100 K. These facts indicate that interest surface layers can be formed by controlling incident energy of oxygen molecular beams and surface temperature.
