We have performed MeV-ion irradiation of high-quality epitaxial ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ films (thickness ≊200 nm) at low temperatures (60 to 80 K) with in situ measurements of the resistivity ρ and the critical temperature ${\mathit{T}}_{\mathit{c}0}$. The increase of ρ and the decrease of ${\mathit{T}}_{\mathit{c}0}$ observed for irradiation with 6-MeV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and 25-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ are proportional to the calculated number of atoms displaced by processes of the nuclear energy loss ${\mathit{S}}_{\mathit{n}}$. For 25-MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, 120-MeV ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$, 173-MeV, and 360-MeV ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$, however, a much stronger sensitivity to irradiation is observed than would be expected from these calculations. Furthermore, ρ and ${\mathit{T}}_{\mathit{c}0}$ depend nonlinearly on ion fluences in the cases of 173- and 360-MeV ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$. The enhanced sensitivity to irradiation and the deviations from linearity are attributed to effects of additional defects induced by the electronic energy loss ${\mathit{S}}_{\mathit{e}}$. If ${\mathit{S}}_{\mathit{e}}$ exceeds an effective threshold ${\mathit{S}}_{\mathit{e}0}$ of 2000 eV/Å, latent tracks of amorphized material are observed. A model is proposed that qualitatively describes the effects of these tracks on transport properties.

• Received 27 February 1990

DOI:https://doi.org/10.1103/PhysRevB.42.4135