Characterization of epitaxial SrTiO3/YBa2Cu3O7 layers deposited on (001) MgO by laser ablation

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Abstract
We discuss the results obtained for SrTiO3/YBa2Cu3O7 layers deposited on (001) MgO substrates by UV pulsed laser ablation. Different samples were prepared to study both the growth of a thin (55 nm) layer of SrTiO3 on MgO and the successive epitaxy of a 220 nm YBa2Cu3O7 (YBCO) film on the SrTiO3 layer. An x-ray diffraction (XRD) texture analysis is reported for the bilayers together with resistivity versus temperature and critical current density (Jc) measurements of the superconducting films. The results show that YBCO grains grow with c-axis normal to the surface; the main in-plane orientations are [100] MgO // [100] SrTiO3 // [100] YBCO ([010] YBCO). The XRD line broadening analysis suggests that YBCO columnar grains grow along the whole thickness of the film, also evidencing dislocations and/or faulting separated by a mean distance of 80 nm. The values obtained for the critical current of the superconductor demonstrate the effectiveness of the SrTiO3 intermediate layer in improving the structural quality of the YBCO film.