Hitoshi Otsu

Electron microscopy of fine holes in polyethyleneterephthalate films irradiated by fission fragments

Fine holes in polyethyleneterephthalate films prepared by exposing to fission fragments and chemical etching were observed with an electron microscope. Transmission electron micrographs of the films 6−9 μm in thickness were taken using a high−voltage electron microscope. Hole densities ahd hole diameters were determined and found to agree with the values calculated from the irradiating condition and those obtained from the measurements of gaseous diffusion through the films, respectively.

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.