Polarization reversal and capacitance-voltage characteristic of epitaxial $Pb(Zr,Ti)O3$ layers

Capacitance-voltage $(C–V)$ measurements were performed on epitaxial layers of $Pb(Zr0.2Ti0.8)O3$ (PZT) with top and bottom $SrRuO3$ (SRO) electrodes. It is shown that the sharp capacitance peak∕discontinuity which is present in the $C–V$ characteristics at different frequencies is directly associated with the polarization reversal. The ferroelectric film is assumed as a large band-gap semiconductor with Schottky contacts at the metal-ferroelectric interfaces. The capacitance discontinuity at the reversal (coercive) voltage is associated with a discontinuity in the built-in potential at the PZT∕SRO interfaces. The $C–V$ characteristics for voltage ranges outside the coercive values can be used to extract the free carrier concentrations as in the case of Schottky metal-semiconductor contacts. The carrier concentration was found to be $(2–4)×1018cm−3$⁠, independent of measuring frequency and temperature up to 1 MHz and 170 °C, respectively, suggesting completely ionized shallow impurities.