Superconducting properties and crystallinity of as-grown MgB/sub 2/ thin films synthesized using an in-plane-lattice near-matched epitaxial buffer layer

As-grown MgB/sub 2/ thin films were synthesized at a low temperature of 270/spl deg/C on an in-plane-lattice-near-matched TiZr buffer layer grown on Al/sub 2/O/sub 3/-C substrate and Al/sub 2/O/sub 3/ substrate without buffer. The critical temperature (T/sub c/), critical current density (J/sub c/) and crystallinity of MgB/sub 2/ on TiZr buffered substrates were found to be high compared with those of MgB/sub 2/ on Al/sub 2/O/sub 3/; the improved T/sub c/ was around 35 K and J/sub c/ 6.6/spl times/10/sup 5/ A/cm/sup 2/ at 5 K under the magnetic field of 1 T perpendicular to the film surface. The epitaxial relationship of MgB/sub 2/ thin film on buffer layer was MgB/sub 2/[01-10]/spl par/TiZr[01-10]/spl par/Al/sub 2/O/sub 3/[11-20], but MgB/sub 2/ thin film without buffer layer had no epitaxial relationship.