Correlations between film properties and microwave surface resistance for YBa2Cu3O7−δ thin films on MgO

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Abstract
Epitaxial YBa2Cu3O7−δ thin films grown by laser ablation on MgO (100) substrates were investigated for microwave applications. By systematically varying the growth conditions, we obtained films with various microstructures, low‐frequency superconducting properties, and microwave performance. The surface resistances were determined from a measured unloaded quality factor in a 8.6‐GHz microstrip resonator. Surface resistance was found to correlate most directly with the degree of grain alignment as revealed by electron channeling and x‐ray diffraction studies. Films grown at optimal conditions gave a scaled surface resistance of 0.6 mΩ at 77 K and 10 GHz.