IMPROVEMENT IN PERFORMANCE OF ELECTRICALLY TUNABLE DEVICES BASED ON NONLINEAR DIELECTRIC SRTIO3 USING A HOMOEPITAXIAL LAALO3 INTERLAYER

Improved structural and dielectric properties of nonlinear dielectric SrTiO3 thin films on LaAlO3 substrates were accomplished by incorporat ing a homoepitaxial LaAlO3 interlayer between the substrate and the di electric film. Using this interlayer, the duality factor of SrTiO3 fil ms with high-temperature superconducting YBa2CU3O7-x electrodes on LaA lO3 substrates was improved by more than 50% at 4.2 GHz and 4 K. This improvement, combined with no change in nonlinearity, led to greater t han a 50% enhancement of the finesse factor (defined as the product of the quality factor and the fractional shift resonant frequency) for t he coplanar waveguide microwave resonators. The reduced planar defect density in the SrTiO3 films was attributed to this improvement. (C) 19 98 American Institute of Physics.