Dual mode cross slotted filter realized with double-sided Tl2Ba2CaCu2O8 films grown by MOCVD

We report on the realization of dual mode microwave filters based on Tl2Ba2 Ca1Cu2O8 (Tl-2212) double-sided superconducting films. The Tl-2212 samples have been grown ex situ on 10 x 10 mm(2) LaAlO3 (100) substrates by a combi ned approach of metal-organic chemical vapour deposition (MOCVD) and thalli um vapour diffusion. Their morphological, compositional and structural natu res have been investigated by scanning electron microscopy, energy dispersi ve x-ray analyses and x-ray diffraction characterization. Both sides of the films are smooth, homogeneous in thickness and composition and show epitax ially-grown Tl-2212 phases. Typical values of T-c = 100 K and J(c) = 0.05 M A cm(-2) at 77 K have been inductively measured for both sides. Microwave m easurements have been performed at 20 GHz by using a dielectric resonator. Two planar superconducting single-stage dual mode filters operating in the C-band with 1% and 10% fractional bandwidth have been realized. The basic e lement of the device is a square patch resonator diagonally crossed by uneq ual slots providing both a size reduction and a simple and controllable way to couple the two degenerate modes. Device response has been studied at di fferent temperatures, performing power and intermodulation measurements. In view of practical applications, the results are compared with those obtain ed by a filter based on high-quality YBCO films.