Shigemi Furuno

Comment to the images of silicon in 〈110〉 orientation

Abstract The comment to some criticism about our images of 〈110〉-oriented silicon is presented to confirm that the observed images represent the correct atom positions with a reasonable accuracy.

Localization of electron current density and its effect on damage production in a molybdenum crystal

Abstract Three-dimensional, fine distributions of electron current density in a molybdenum crystal are examined by the many-beam dynamical theory of electron diffraction for electrons incident parallel to the principal zone axes. It is found that the two-dimensional distribution in the transverse plane oscillates along the depth direction, and that a highly localized distribution around the rows of atoms and an almost flat distribution appears alternatively with definite periods of depth. The effect of the localized current density on the damage production is discussed by introducing the “effective current ratio”, J eff which is defined as the ratio of the local current density at the rows of atoms to the mean current density for electrons incident parallel to the zone axis. The values J eff for the incidence of 1 MeV electron are found to increase in the order of the (111), (001) and (110) directions. The energy dependence J eff is also examined for the (001), (110) and (111) axial cases respectively.

Experimental Determination of Depth Distribution Function of Carbon Kα-Rays

The depth distribution functions (ρx) of carbon Kα-rays are determined by the experiment using carbon films of stepwise shape deposited on several kinds of substrates with atomic numbers close to that of carbon. Some results are presented for both (ρx) and X-ray intensity function f(χ) at accelerating voltages of 5, 10 and 15 kV. It is found that Philiberts formula for f(χ) fits the present results by using suitable combinations of parameters involved.

Electron energy loss spectroscopy on oxygen k-edge fine structure of YBa2Cu3Oycontaining dopants (La, Ca, Co)

The fine structures of the oxygen K-edge in the Y-Ba-Cu-O system, in which hole content was controlled by reducing the oxygen content and doping elements (La, Ca and Co), were investigated by electron energy loss spectroscopy (EELS). When Ba(+2) and Y(+3) were replaced by La(+3) and Ca(+2), respectively, the oxygen content of the sample changed and the peak corresponding to the hole state near the Fermi energy sensitively changed with the average hole content. When Cu(+2) was replaced by Co(+3), Tc decreased drastically and the peak at the oxygen K-edge shifted to higher energy.

In-Situ Observation of Bubbles in Superconductor YBa2Cu3O7-δ Materials During He Ion Irradiation in an Electron Microscope

In-situ observation of formation and growth of bubbles in superconductor YBa2Cu3O7-δ materials during 10 keV He ion irradiation was carried out using a transmission electron microscope. Irradiations were performed inside the electron microscope linked with an ion gun at room temperature. The images on the fluorescent screen were recorded by VTR. The small bubbles were observed at the fluence of 9x1016 ions/cm2. These bubbles increased in number and continued to grow, as the irradiation proceeded. At the fluence of 3x1017 ions/cm2 bubbles began to coalesce with each other, followed by blisters and exfoliation. New bubbles were formed underneath, grew and coalesced. Preferential formation and growth of He bubbles at crystal grain boundary were found during the irradiations. It was also found that amorphization of YBa2Cu3O7-δ crystals occurred as the irradiation proceeded.