Graded ferroelectric thin films: Possible origin of the shift along the polarization axis

Abstract

Hysteresis measurements performed on graded Pt/lead zirconate titanate (PZT)/Pt structures with well oxygenated PZT films do not display any shift along the polarization axis (Voffset) as previously reported. On the other hand, when the PZT graded films were grown under low oxygen pressure, an offset voltage was measured. This shift was systematically enhanced after cycling the film as for fatigue measurements. It was also observed that the Voffset is independent of the value of the reference capacitor used in the Sawyer–Tower circuit. We propose an asymmetry in the leakage current of the structure to be at the origin of the shift along the polarization axis.