Fine structure of the tracks of several-tens-MeV Au ions in YBa2Cu3O7-x studied by cross-sectional transmission electron microscopy

Abstract

We studied the morphology of the tracks (irradiation damage) of 44, 66, and 84 MeV Au ions in YBa2Cu3O7-x (YBCO) thin films using cross-sectional transmission electron microscopy (TEM). The electronic energy loss (Se = 11.6, 16.7, and 20.1 keV/nm) ranged near the onset of ion-track formation previously determined by plan-view TEM and critical-temperature measurements (about 13 keV/nm). The morphology changed from 1D arrays of large spheres of about 5 to 10 nm diameter in 44-MeV irradiation to their elongated variant (spheroid) that were statistically pierced by thin-lines of about 1 to 2 nm and 3 to 5 nm diameter in 66 and 84 MeV, respectively. In the same series of Au-irradiated YBCO films, we observed a sudden increase in critical current density at self-field and 77 K between 44- and 55-MeV irradiation, in agreement with the appearance of the thin-line damage in TEM (between 44- and 66-MeV).