In situ grown superconducting YBCO films on buffered silicon substrates for device applications

Thin films of YBa₂Cu₃O_7– (YBCO) have been grownin situ on silicon single-crystal (100) substrate by using SrTiO₃ as a buffer layer. The deposition has been carried out by on-axis rf magnetron sputtering method. The deposition condition have been optimized by studying the plasma characteristics and correlating them with the superconducting performance of the film. Films deposited at substrate temperature in the range of 680–700°C from stoichiometric YBCO targets in an argon + oxygen mixture (31) are superconducting and showc-axis epitaxy. Compositional confirmation has been carried out using Rutherford backscattering. Scanning tunneling microscopy of the films reveal formation of well-defined layered structure with some defects in the initial stages ofin situ growth of the films. Films grown on SrTiO₃ substrates have excellent crystalline quality (XRD), transition temperatureT _c0=81 K and the critical current densityJ _c >2×10⁵ A/cm² for unpatterned films at 77 K. On silicon substrates using buffer layers thein situ deposited YBCO films shows a higher transition width andT _c0 is also slightly less (71 K).