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

Abstract

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.