Reversible and irreversible domain wall contributions to the polarization in ferroelectric thin films

In this work, standard characterization methods like hysteresis loops and C-V- measurements are used to distinguish the reversible and irreversible parts of the total ferroelectric polarization. Special attention has been given to the frequency dependence of the hysteresis loops- and the C-V-measurements. The frequency dependence of the C-V measurements indicates that the relaxation of the polarization is enhanced in ferroelectric materials compared to paraelectric SrTiO3. The reversible and irreversible contributions are demonstrated for SrBi2Ta2O9 thin films and Pb(Zr,Ti)O-3 thin film capacitors. Additionally, a method is described to obtain the static hysteresis curve, which allows to characterize the polarization of a ferroelectric material independent of the measuring frequency, since remanent polarizations or coercive voltages inferred from usual hysteresis loop measurements strongly depend on the measuring frequency.