Variations in the Structural, Morphological and Microwave Properties of YBa₂Cu₃O7-δ Films on Etching

Various etching techniques have been used for making high-temperature superconductor (HTS) circuits and devices for electronic applications and to reduce the film thickness for investigating the thickness dependence of the critical current density Jc of HTS-coated conductors. We studied the effects of wet-chemical etching and Ar-ion milling on the structural, morphological and microwave properties of YBa₂Cu₃O7-δ (YBCO) films grown on LaAlO₃ substrates. Br₂ in methanol (Br₂-MeOH), nitric acid and disodium ethylenediaminetetraacetic acid (EDTA) were used as the etchants for the wet etching process. The lattice constant and the surface roughness of the YBCO films were measured before and after etching along with the microwave surface resistance (RS) at~8.5GHz. Variations in the YBCO film thickness on etching were considered to compare the intrinsic RS values of YBCO films before and after etching with the effects of finite film thickness taken into account. Both disodium EDTA and Br₂-MeOH appeared to be suitable as etchants with the observed increases in the c-axis constant, the rms surface roughness and the intrinsic RS being less than 0.04 %, 19 % and 5 %, respectively, after etching. Meanwhile, YBCO films etched with Ar-ion milling and nitric acid showed significant degradation in the properties with variations of 55 % and 25 % in the intrinsic RS observed after etching, respectively. A small, but nevertheless enhanced, intrinsic RS was consistently observed for YBCO films etched by either Br₂-MeOH or disodium EDTA throughout the measured temperatures. KCI Citation Count: 2