MOD growth of epitaxial cerium oxide buffer layer on LAO substrates for fabrication of c-axis oriented YBCO

Epitaxial cerium oxide (CeO₂) buffer layer has been grown on lanthanum aluminate (LAO) single crystal substrates for fabrication of c-axis oriented YBa₂Cu₃O_7-x (YBCO). Precursor solution of cerium acetylacetonates with viscosity of 0.6 centipoises was spin coated on the 1×1×cm area LAO substrates. The calcination was carried out by very slow ramp (1×C per minute) until the final temperature of 500×C in oxygen flow to remove most of the organic compounds. The final heat treatment has been done at 780×C by a ramp of 20× per minute in gas flow of mixed argon×oxygen with 5×Pa partial pressure of oxygen. The thickness of the deposited CeO₂ buffer layer was 20 nm. Then, 100 nm thick YBCO film was deposited by sputtering on the CeO₂ buffered LAO substrate. Another film with same deposition conditions was also fabricated on the bare LAO crystal for comparison. The scanning electron microscopy (SEM) and X-ray diffraction characterisations show a/b axis YBCO decreases significantly when using the CeO₂ buffered LAO instead of the bare LAO. R-T and J_c measurements of the samples are also reported. Superconducting transition width of the fabricated film on the substrate with CeO₂ buffer layer is less than 0.4 K and the J_c of the fabricated film is above 3.5 MA/cm².