Contribution of domain motion to the dielectric properties of ferroelectric thin films

The variations of polarization and dielectric properties with the grain size of PZT films have been investigated experimentally and theoretically. It is revealed that polarization increases much more quickly with the grain size than dielectric constant does. The polarization increases as the grain size increases and is saturated when the grain size is about 60 nm, whereas the dielectric constant is saturated when the grain size is about 70 nm. Because the dielectric response of ferroelectrics is affected by the domain switching and exhibits hysteresis, the contribution of domain dynamics to the dielectric properties must be considered. Varying grain size will change the domain dynamics due to the close relationship of domain width and grain size. Based on the Landau-Ginzburg (LG) model, the variations of remnant polarization and dielectric constant against grain sizes have been investigated, considering the contribution of domain motion. The calculation result is consistent with the experimental result.