YBCO thin film sputtering: an efficient way to promote microwave properties

To obtain high quality YBa₂Cu₃O_7-δ (YBCO) films by on-axis rf-magnetron sputtering, we have undertaken a twofold study: first, we have investigated the role of sputtering plasma parameters (dc self-bias voltage, rf power, oxygen flux and water vapor flux introduced into the plasma) in order to limit resputtering effect. In particular, we have shown the significance of mastering the dc self-bias voltage. Secondly, we have deposited YBCO films on [001] LaAlO₃ substrates taking into account the optimum flux conditions previously determined, and put into light the effect of the substrate temperature. Cross-optimization of the microstructural, electrical and microwave properties has been performed with respect to substrate temperature. A narrow optimal temperature window has been established to obtain films suitable for microwave applications.