Synthesis and microwave properties of Tl2Ba2CaCu2O8 superconducting films grown by MOCVD

We report on the synthesis, structural and electrical characterization of high quality Tl2Ba2Ca1Cu2O8 (Tl-2212) superconducting films. The samples have been grown ex-situ on 10×10 mm2 LaAlO3 (100) substrates by a combined approach of metal-organic chemical vapor deposition (MOCVD) and thallium vapor diffusion. The morphological and compositional nature of the c-axis oriented films has been investigated by SEM and X-ray analyses. Typical values of Tc = 104 K and Jc = 0.5 MA/cm2 at 77 K have been measured. Microwave measurements have been performed at f = 87 GHz inserting the film in a copper cavity and at f = 1.5 GHz on patterned samples using a microstrip resonator technique. A penetration depth !(0) = 400 nm is evaluated by fitting the microwave data with phenomenological equations. The minimum value of the surface resistance Rs measured at 4.2 K is 60 ?" and 6 m" at 1.5 GHz and 87 GHz respectively. The microwave data are described in the context of a modified two fluid model. An evaluation of the temperature dependence of the scattering rate has been performed through the simultaneous measurement of the surface resistance and the penetration depth.