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 CeO
₂
coated r-cut sapphire substrates. An in situ two-temperature deposition process was introduced in the growth of CeO
₂
buffer layers. XPS measurements showed that the deposition process can sharply decrease the mutual diffusion at the interface. The critical temperature T
_c
of Tl-2212 film grown on the buffer layer was 108.2 K, the critical current density J
_c
(77K, 0T) was above 6 MA/cm
²
, and the microwave surface resistance R
_s
(77K, 10 GHz) was below 200 μΩ.