EFFECT OF OXYGEN DEFECTS ON TRANSPORT-PROPERTIES AND T-C OF YBA2CU3O6- DISPLACEMENT ENERGY FOR PLANE AND CHAIN OXYGEN AND IMPLICATIONS FOR IRRADIATION-INDUCED RESISTIVITY AND T-C SUPPRESSION(X )

The effect of electron irradiation with energy from 20 to 120 keV on t he resistivity, Hall coefficient, and superconducting critical tempera ture T-c of YBa2Cu3O6+x thin films has been studied. The threshold ene rgy of incident electrons for T-c suppression has been found, and the displacement energy for oxygen in CuO2 planes has been evaluated as 8. 4 eV for irradiation along the c axis. The kinetics of production of t he in-plane oxygen vacancies has been studied and found to be governed by athermal recombination of vacancy-interstitial pairs. The evaluate d recombination volume constitutes about 21 unit cells. The increase i n the T-linear resistivity slope and Hall coefficient at unchanged T-c was observed in irradiations with subthreshold incident energies and was ascribed to the effect of chain oxygen displacements. The upper li mit on the displacement energy for chain oxygen has been estimated as 2.8 eV. In x=0.9 samples the T-c suppression by in-plane oxygen defect s and increase in residual resistivity have been found to be, respecti vely, -280 K and 1.5 m Omega cm per defect in the unit cell. It is sho wn that T-c suppression by in-plane oxygen defects is a universal func tion of the transport impurity scattering rate and can be described qu alitatively by pair-breaking theory for d-wave superconductors with no nmagnetic potential scatterers. Evaluation of scattering and Fair-brea king rates as well as the scattering cross section and potential is gi ven. A comparison of the influence of in-plane oxygen defects on trans port properties with that of other in-plane defects, such as Zn and Ni substitutions for Cu, is also made.