.3 Inch Ybco Double-sided Superconducting Films Developed

The most promising application of high-TC superconducting thin films is passive microwave devices and the fabrication of large-area double-sided YBCO thin films is a convenient way to realize large scale production and multi-component integration. A systematic methodology has been proposed to investigate the feasibility of the manufacture of ?3" double-sided YBCO thin films by inverted cylindrical sputtering(ICS) with bi-axial substrate rotation.Some important considerations of a vacuum have been discussed and the influence of inlet gases on heat transfer was found to be negligible at the optimized deposition parameters. A model based on radiation heat transfer is developed to evaluate the homogeneity of some heater designs and a cylindrical heater that is composed of two heating parts with individual power inputs was constructed for the ?3" biaxial rotating substrate. By modulating the input powers of the two heating parts, a homogeneous temperature distribution over ?3" is realized, the deviation of which is less than ±5℃.In order to enhance the thickness homogeneity of ?3" thin films, the transportation of sputtered particles has been investigated. The mean free paths of Y, Ba, and Cu at the optimized gas pressure are less than 0.7mm, and therefore, they are transported mainly by diffusion in the sputtering gas. A speed-modulated bi-axial rotation method has been presented, by which the thickness deviation of ?3" thin films is reduced to less than 5%.?3" double-sided YBCO samples have been fabricated, and the basic properties are measured: the samples are strictly c-axis epitaxial and FWHMYBCO(005) < 0.3°. TC ranges from 89.8K to 90.2K and jC is about 2.14~2.50MA/cm2. Microwave surface resistances measured by confocal resonator and dielectric resonator are 50~75m?(145GHz, 75K) and 0.6m?(8.5GHz, 77K), respectively.In order to investigate the influence of the special processing parameters on thin film growth, the growth mechanism of YBCO on large-area substrate has been studied. The initial growth direction of YBCO is almost independent of substrate temperature at the range of 720℃~800℃. All the grains are c-axis oriented and no a-axis grains have been detected. Further, high deposition temperature or large temperature fluctuation results in high nucleate density. Obvious screw growth mode and steps with one-unit-cell height have been observed at the optimized deposition condition.