Preparation and characterization of YBCO thin films on silicon

We have prepared thin films of superconducting YBa₂Cu₃O₇ on bare silicon (100) by thermal co-evaporation of yttrium, barium and copper in an oxygen atmosphere. The temperature never exceeds the deposition temperature of about 650°C. No post-deposition annealing is necessary to achieve superconductivity at 85 K and critical current densities, at 4.2 K, of 9 × 10⁴ A cm^-2. X-Ray diffraction studies show that the best films are oriented with the c axis perpendicular to the substrate, with no trace of reflections other than those from (00l) planes. We have also produced c axis oriented superconducting YBCO films on silicon substrates with buffer layers of amorphous SiO₂ and amorphous Si₃N₄. The best superconducting characteristics of these films were transition temperatures of 68-69 K and critical current densities at 4.2 K of 3 × 10³ A cm^-2.