ION IRRADIATION OF EPITAXIAL YBA2CU3O7-DELTA FILMS - EFFECTS OF ELECTRONIC-ENERGY LOSS

We have performed MeV-ion irradiation of high-quality epitaxial YBa2Cu3O7- films (thickness 200 nm) at low temperatures (60 to 80 K) with in situ measurements of the resistivity and the critical temperature Tc0. The increase of and the decrease of Tc0 observed for irradiation with 6-MeV He4 and 25-MeV O16 are proportional to the calculated number of atoms displaced by processes of the nuclear energy loss Sn. For 25-MeV S32, 120-MeV Kr86, 173-MeV, and 360-MeV Xe129, however, a much stronger sensitivity to irradiation is observed than would be expected from these calculations. Furthermore, and Tc0 depend nonlinearly on ion fluences in the cases of 173- and 360-MeV Xe129. The enhanced sensitivity to irradiation and the deviations from linearity are attributed to effects of additional defects induced by the electronic energy loss Se. If Se exceeds an effective threshold Se0 of 2000 eV/, latent tracks of amorphized material are observed. A model is proposed that qualitatively describes the effects of these tracks on transport properties. © 1990 The American Physical Society.