Conspicuous Voltage Shift of D-E Hysteresis Loop and Asymmetric Depolarization in Pb-Based Ferroelectric Thin Films

Polycrystalline Pb(Zr,Ti)O 3 (PZT) thin films fabricated by a chemical solution deposition (CSD) process exhibited a conspicuous initial voltage shift in the D - E hysteresis loop toward the negative-bias field. It was concluded that the origin of the voltage shift was an internal bias field due to asymmetric space-charge distribution induced by the natural alignment of spontaneous polarization during the cooling process. The internal bias field also caused asymmetric depolarizaiton at the zero-bias field. In heteroepitaxial (Pb,La)TiO 3 thin films, we observed a conspicuous voltage shift toward the positive-bias field and asymmetric depolarization at the zero-bias field. They were eliminated by the application of a positive unipolar pulse train.