Remanent polarization reduction with enhanced temperature in ferroelectric thin films

摘要

The remanent polarization reduces monotonically with the rising temperature from 295 to 430 K in Pt/IrO_2/Pb(Zr_(0.4)Ti_(0.6))O_3/IrO_2/Pt thin-film capacitors, although the saturation polarization of the films is nearly constant in the temperature range. Fast-pulse measurements of polarization retention shortened on the order of domain switching time indicate a rapid increase in the remanent polarization, which suggests backswitching of partial domains after the applied field with a long relaxation time. The qualitative modeling of domain switching currents predicts the presence of interfacial passive layers near top and bottom electrodes with damaged ferroelectricity, and the density of backswitched domains enhances with the elevated temperature along with reductions in both coercive voltage and interfacial capacitance, whereas the whole dielectric capacitance of the films increases abnormally, in agreement with the argument of the reversible domain contribution to the large dielectric permittivity in ferroelectrics. It is believed that the presence of interfacial passive layers can build in an opposite internal field to backswitch partial domains after the field. Therefore, the ultimate remanent polarization depending on the product of coercive voltage and interfacial capacitance reduces with the elevated temperature.