Superconducting properties and crystallinity of as-grown MgB2 thin films synthesized using an in-plane-lattice near-matched epitaxial buffer layer

As-grown MgB₂ thin films were synthesized at a low temperature of 270°C on an in-plane-lattice-near-matched TiZr buffer layer grown on Al₂O₃-C substrate and Al₂O₃ substrate without buffer. The critical temperature (T_c), critical current density (J_c) and crystallinity of MgB₂ on TiZr buffered substrates were found to be high compared with those of MgB₂ on Al₂O₃; the improved T_c was around 35 K and J_c 6.6×10⁵ A/cm² at 5 K under the magnetic field of 1 T perpendicular to the film surface. The epitaxial relationship of MgB₂ thin film on buffer layer was MgB₂[01-10]||TiZr[01-10]||Al₂O₃[11-20], but MgB₂ thin film without buffer layer had no epitaxial relationship.