Influence of sequential etching on YBCO films deposited by PLD from a nanostructured target

Thin YBa/sub 2/Cu/sub 3/O/sub 6+x/ (YBCO) films with T/sub c/ = 90 K and high critical current in the order of 10/sup 7/ A/cm/sup 2/ at 77 K are prepared with pulsed laser deposition from a nanostructured target. Changes in the superconducting and structural properties of the films are investigated after repeated thinning by Ar-ion sputtering or by electrochemical etching. As shown by Auger depth profiling, the chemical composition is preserved through the film during Ar-ion sputtering while electrochemical etching changes the atomic concentrations and surface structures. Investigations by SQUID magnetometry and by conventional resistivity measurements give evidence that the dependence of T/sub c/ on the film thickness is similar to as-prepared ultrathin films. The thickness dependence of J/sub c/ indicates an excess of pinning centers on the surface of the as-deposited film.