Growth and characterization of Pb( Zr,Ti)O-3 thin films and ferroelectric polarization charging of YBa2Cu3O7 thin films

Pb(Zr,Ti)O-3 (PZT) thin films were epitaxially grown on MgO(100) and SrTiO3 (100) single crystal substrates and on YBa2Cu3O7(001) (YBCO) sublayers by e mploying reactive inverted cylindrical magnetron sputtering. The Pb content and Zr/Ti ratio of the PZT films were analyzed by Rutherford backscatterin g spectrometry as a function of the deposition temperature and the sputteri ng pressure. The film orientation perpendicular to and in the substrate pla ne and the respective mosaic spreads were determined by X-ray diffraction. The electrical insulation and the temperature- and frequency-dependent diel ectric permittivity of the PZT films were studied on ferroelectric capacito rs. The largest remanent polarization of 61 muC/cm(2) at 77 K was obtained for films with the correct Pb stoichiometry and the highest degree of epita xy. Three degradation effects of PZT capacitors with Au top and YBCO bottom electrodes, namely fatigue, loss of retention and aging, were also investi gated. The fatigue tests revealed a rather poor endurance of the capacitors . The loss of retention and aging, however, were negligible at an operation al temperature of 77 K. Ferroelectric polarization charging effects were ob served in YBCO films thinner than 20 nm. While the resistance modulation of 4% and its polarity dependence were consistent with a charging effect and the p-type conduction in YBCO, the modulation of the critical current densi ty of 3% was significantly smaller than expected from the polarization swit ching of PZT. (C) 2001 Elsevier Science B.V. All rights reserved.