Ferroelectric field effect in YBa2Cu3O7-δ thin films

Ferroelectric superconductor field effect transistors (FSuFETs) consisting of YBa2Cu3O7-delta (YBCO) channels and Pb(Zr0.54Ti0.46)O-3 (PZT) gate insulators were fabricated. In order to prevent degradation of the YBCO layer, a thin SrTiO3 (STO) buffer layer was inserted between YBCO and PZT. The PZT films were epitaxially grown and revealed high remanent polarizations of up to 61 mu C/cm(2). Ferroelectric polarization charging effects were observed in YBCO channels thinner than 20 nm. Modulations of the resistivity, the critical temperature and the critical current density clearly reflected the ferroelectric hysteresis of the PZT layer. The changes amounted up to 10%, 1 K and 16%, respectively. The modulations and their polarity dependency were consistent with a charging effect and the p type conduction in YBCO. Reversing the polarization state led to a nonvolatile change of the YBCO properties. (C) 1999 Elsevier Science B.V. All rights reserved.