Resonators and filters made of YBaCuO thin films on sapphire wafers

300 500 nm thick YBaCuO thin films with c-axis orientation were simultaneou sly deposited by sputtering of sintered hollow cylinders on both sides of C eO2 buffered r-cut sapphire wafers with a diameter of 3 inch. Microstrip re sonators and filters were manufactured to study the microwave properties of the films at 77 K in the frequency band from 2 to 6 GHz which is relevant to satellite communication. At linear response the resonance curve of the t ransmission resonators could perfectly be described by a Lorentz function. Very high values of the unloaded quality factor, Q(u), of up to 32 000 were reached at 4 GHz. At nonlinear response Q(u) decreased due to the power de pendence of the surface resistance of the YBaCuO films which steeply increa sed at an oscillating power of several watts corresponding to a critical su rface magnetic field of about 10 mT. The seven- and three-pole bandpass fil ters with center frequencies of 6 and 2 GHz, respectively, showed a low att enuation of less than -0.3 dB in the pass band. The results manifest that s puttering is a qualified and reliable method for large-area deposition of Y BaCuO thin films which are suitable for microwave applications. (C) 2001 El sevier Science B.V. All rights reserved.