Structure of beam tracks induced by swift heavy ions in BiSrCaCuO superconductors

Sasase, Masato*; Okayasu, Satoru  ; Yamamoto, Hiroyuki; Kurata, Hiroki*; Hojo, Kiichi

Columnar defects are produced in semiconducting and insulating materials by swift heavy ion irradiation. In the present study, we investigate the columnar defects produced in the BiSrCaCuO superconductor by the heavy ion irradiation (Au, I, Br, Ni) in the energy range of 60-600 MeV. On the basis of the transmission electron microscopy, it is shown that the diameters of columnar defects become smaller and their distributions become narrower with the ion velocity. These facts are explained as the effect of nuclear collision by calculating the mean free path for the irradiated ions. Present results imply the nuclear collisions strongly affect the columnar defect formations even for the swift heavy ion irradiation.