High-T/sub c/ superconducting EuBa/sub 2/Cu/sub 3/O/sub y/ thin films and MgO and YAlO/sub 3/ for coplanar devices

The authors have studied the microwave properties of high-T/sub c/ superconducting EuBa/sub 2/Cu/sub 3/O/sub y/ (EBCO) films on MgO and YAlO/sub 3/ substrates with low dielectric constants ( in =10 and 16, respectively), and a low loss tangent (tan delta <10/sup -5/). Measurements of surface resistance R/sub s/ at 50 GHz in a cavity show that EBCO films exhibit low R/sub s/ values (77 K) of 2-10 m Omega . A microstructural study using transmission electron microscopy showed that crystal defects related to the in-plane misorientation are observed for films with higher R/sub s/ values. The R/sub s/ values of the patterned films were measured in a coplanar transmission line resonator. A typical value for patterned films was 28 mu Omega at 4 GHz and 28 K.<
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