Polarization and self-polarization in thin PbZr_1-<i>x</i>Ti_<i>x</i>O₃(PZT) films

Abstract

The self-polarization effect in ferroelectric thin films has been studied for PZT films 0.5-1 µm thick deposited by radio-frequency magnetron sputtering of various ferroelectric ceramic targets (Zr/Ti = 54/46, Zr/Ti = 54/46 + 10% PbO and Zr/Ti = 40/60 + 10% PbO). The laser intensity modulation method has been applied, together with the methods of C-V characteristics and dielectric hysteresis loops, to determine the polarization distribution and evaluate the built-in electric fields in the films. It is shown that the bottom interface of the thin-film Pt-PZT-Pt capacitor structure is the source of self-polarization for a certain technological sequence of structure formation. The self-polarization effect is caused by two factors: (i) n- or p-type conductivity due to oxygen or lead vacancies or other impurities in the films and (ii) high trap density at the bottom interface of the structure.