Novel stage in fabrication of as-grown MgB2 films by adopting Ti seed layer

We report that Ti buffer layer improves the structural quality and superconducting properties of MgB2 film deposited on ZnO (0 0 0 1) and Al2O3 (0 0 0 1) substrates using molecular beam epitaxy. It was found that Ti layers were grown epitaxially on the substrates and the MgB2 films were c-axis oriented with two types of in-plane orientations. The crystal quality measured by the rocking curve width of X-ray diffraction peak was improved and superconducting transition temperature increased as the buffer layer thickness increased on both substrates. The highest Tc observed in this study was 37 K and 35 K in the film deposited on the Ti buffer layer 50 nm thick with the ZnO and Al2O3 substrates, respectively