EFFECTS OF ETCHING ON THE MORPHOLOGY AND SURFACE-RESISTANCE OF YBA2CU3O7-DELTA FILMS

The changes in surface morphology and surface resistance of sputtered and laser ablated YBa2Cu3O7-delta films both before and after etching have been examined. Six different etchants were used: citric acid, nit ric acid, Br-methanol, EDTA, disodium EDTA, and ion milling. The surfa ce morphologies of the films were examined by reflection high energy e lectron diffraction (RHEED) and atomic force microscopy (AFM), both be fore and after etching. The surface resistance (R(s)) was measured at 94 GHz using a confocal resonator. An amorphous layer was found on the film surfaces after exposure to air. A few of the etches restored som e of the surface crystallinity, but most caused increases in the overa ll surface roughness. Several of the wet etches attacked dislocations. Ion milling caused the largest degradation of surface crystallinity a nd a corresponding increase in R(s). Some of the chemical etches incre ased R(s) by less than 15%.