Fabrication of CeO2 buffer layers for epitaxial growth of Tl-2212 films by the in situ two-temperature process

High-quality Tl-2212 superconducting films were prepared on CeO2 coated r-cut sapphire substrates. An in situ two-temperature deposition process was introduced in the growth of CeO2 buffer layers. XPS measurements showed that the deposition process can sharply decrease the mutual diffusion at the interface. The critical temperature Tc of Tl-2212 film grown on the buffer layer was 108.2 K, the critical current density Jc (77K, 0T) was above 6 MA/cm2, and the microwave surface resistance Rs(77K, 10 GHz) was below 200 μΩ.