Nonlinear microwave properties of YBaCuO thin films studied with the coplanar resonator technique

An experimental study of the nonlinear effects in high temperature superconducting thin films, as a function of temperature and incident microwave power is performed. Three YBaCuO based coplanar resonators made by different techniques have been characterized. A parameter, defined as the relative variation of the unloaded quality factor between a low and a high microwave incident power, has been introduced to quantify the variation of the nonlinear effects with temperature. Results show a good correlation between measurements of the nonlinear surface resistance and the films morphology observed by scanning electron microscopy. (C) 2002 Elsevier Science B.V. All rights reserved.