Simulation of radial flow generated by rotating a set of screens and disks, 2

Ogiwara, Norio

Journal of the Vacuum Society of Japan, 54(3), p.188 - 191, 2011/03

https://doi.org/10.3131/jvsj2.54.188

Study on surface oxidation reactions of TiAl by synchrotron radiation X-ray photoemission spectroscopy

Hashinokuchi, Michihiro*; Sumimoto, Yuichi*; Tode, Mayumi; Okada, Michio*; Harries, J.; Teraoka, Yuden; Kasai, Toshio*

no journal, , 

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 on the translational energy of incident O molecules. The present results suggest that the oxidation on a TiAl surface proceed via molecular adsorption as a precursor state.

Surface topography depending on translational kinetic energy of O in oxidation of Si(111)-77 at 300 K

Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

no abstracts in English

Structure and phase transition of one-dimensional atomic chain on Pt/Ge(001) surface by reflection high-energy positron diffraction

Mochizuki, Izumi; Fukaya, Yuki; Kawasuso, Atsuo

no journal, , 

Quasi one dimensional (1D) metallic chain of single-atomic wide is constructed on the Ge(001) surface by the adsorption of Pt with 1/4 atomic layer. While the atomic chain is required the elucidation of the electronic properties about the 1D metal behavior or the metal-insulator transition, there is also discussed about the atomic arrangement. The Pt chain or the Ge chain models have been proposed in the recent theoretical calculations, but that is still to be determined because of scarce experimental validation. We have measured the reflection high energy positron diffraction (RHEPD) for the elucidation of the atomic arrangement of the 1D chain on the Pt/Ge(001) surface. Hence the beam intensity of the RHEPD rocking curves is very sensitive to the topmost surface structure, we can estimate that based on dynamical diffraction theory. We observed the enhancement of the specular reflection of the rocking curve with the glancing angle of 23, which indicates the construction of the atomic chain structure on the Pt/Ge(001) surface. We will discuss the structure analysis of the 1D chain and the phase transition of the low temperature.

Growth temperature dependence and Si-doping effect on vacancy-type defect structure in MBE-grown GaCrN films

Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo; Hasegawa, Shigehiko*; Zhou, Y.*; Asahi, Hajime*

no journal, , 

In the MBE growth of the GaCrN dilute magnetic semiconductor films, low temperature (LT) growth is important in order to dope Cr atoms to high concentration. However, the problem with LT growth is the formation of lattice defects in the films. In this study, we have investigated growth temperature dependence and Si-doping effect on vacancy-type defect structure in MBE-grown GaCrN films probed by a slow positron beam. As a result, LT-grown undoped GaCrN film indicates a high value of positron annihilation parameter which implies the existence of vacancy-type defects. Furthermore, the positron annihilation parameter value was decreased by Si doping. First principle calculations of annihilation -ray spectra revealed that both of the detected defects from the undoped LT-GaCrN and from the Si-doped LT-GaCrN film were vacancy clusters (V-V) and VN-related defects, respectively.

Relationships between surface thermal degradation and D thermal desorption of hydrogen storage alloys VCrTi and TiFe

Tode, Mayumi; Harries, J.; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

In order to study the relationships between the thermal desorption of hydrogen and the surface layer, we have used high-resolution synchrotron radiation X-ray photoelectron spectroscopy to study the thermal degeneration processes of the surface layers. The experiments were performed at the JAEA soft X-ray beamline BL23SU at SPring-8, using the "SUREAC2000" surface reaction analysis apparatus. XPS spectra were recorded for room temperature TiFe and V25Cr40Ti35 following flash heating to 373-1073 K. In the un-deuterium implanted TiFe, the photoelectron spectra have changed when heating it at the temperature of 573 K. In the deuterium implanted TiFe, the photoelectron spectra have changed when heating it at the temperature of 473 K. When the deuterium ion was injected, the thermal degeneration temperature of a natural oxide layer was observed to shift to the low temperature side by 150 C.

Real-time XPS observation of oxidation processes on Si alloy surfaces; Comparison of mixing effects of C and Ge

Hozumi, Hideaki*; Kaga, Toshihide*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

In order to clarify the difference of the oxidation reaction mechanism between an SiGe and SiC alloy layer, the real time photoelectron spectroscopy was employed for observing the oxidation rate and behavior of Ge and C atoms during oxidation. The experiments were performed using the surface reaction analysis apparatus placed at the BL23SU of SPring-8. By comparing between the both alloy surfaces, it is found that initial oxidation rate on the SiGe alloy was slower than that on the SiC alloy. Here, only Si atoms were oxidized on the both alloy surfaces. C atoms were condensed at SiO/Si interface and 3C-SiC alloy were formed. Ge atoms were diffused into Si substrate. These facts are resulted in the oxidation-strain-induced point-defect generation, in which C and Ge atoms are exchanged for Si atoms through the vacancies.

Study on oxidation reaction of TiAl surface by synchrotron radiation X-ray photoemission spectroscopy

Hashinokuchi, Michihiro*; Sumimoto, Yuichi*; Tode, Mayumi; Harries, J.; Okada, Michio*; Teraoka, Yuden; Kasai, Toshio*

no journal, , 

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 on the translational energy of incident O molecule. The present results suggest that the oxidation on TiAl surface proceed via precursor molecular states.