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, nitric acid, Br-methanol, EDTA, disodium EDTA, and ion milling. The surface morphologies of the films were examined by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM), both before 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 some of the surface crystallinity, but most caused increases in the overall surface roughness. Several of the wet etches attacked dislocations. Ion milling caused the largest degradation of surface crystallinity and a corresponding increase in R(s). Some of the chemical etches increased R(s) by less than 15%.