IRRADIATION EXPERIMENTS ON HTSC THIN-FILMS

Thin single crystalline REBaCuO films (RE = rare earth) were irradiate d with 300 keV H+ and He+ ions. Investigations of the ion-induced chan ges of the transport and especially of the structural properties were performed. The superconducting properties degrade and the unit cell ex pands under irradiation, whereby the formation of a tetragonal structu re per se is not a condition for a loss of superconductivity. In a-axi s grown films irradiated with protons we observed the formation of a n ew square-root 2a(c) x square-root 2 a(c) x 3a(c) (a(c) almost-equal-t o 3.8 angstrom) superstructure induced by oxygen reordering in the bas al plane of the unit cell. For higher fluences an amorphization proces s sets in probably driven by the existence of long range forces.