For the PZT film under study in the present work, asymmetries of the macroscopic P-E hysteresis loops and the analysis of the local piezoresponse by piezoresponse force microscopy indicated an internal bias electric field which is oriented towards the bottom electrode
This internal electric bias field (not estimated) which is a signature of the self-polarization of the film interferes with the applied extrinsic electric field (max ±127 kV/cm) resulting in an asymmetric effective electric field.
Due to this superposition of the two electric fields the effective electric field is higher in the direction towards the bottom interface than towards the top surface.
As a consequence, higher strains are observed for negative voltages compared to positive voltages leading to asymmetries in the measured butterfly curves (see Fig. 3(c))
. While the effective field for negative applied voltages is sufficient to polarize the film in one direction, it is not clear if the magnitude of the effective electric field for positive applied voltages is large enough to overcome the positive coercive field Ec (+40 kV/cm and −14 kV/cm) and thus to switch the polarization of the studied film [29]. Further experiments are needed to uncover the origin of this behavior.
For the PZT film under study in the present work, asymmetries of the macroscopic P-E hysteresis loops and the analysis of the local piezoresponse by piezoresponse force microscopy indicated an internal bias electric field which is oriented towards the bottom electrode [29, 30].
This internal electric bias field (not estimated) which is a signature of the self-polarization of the film interferes with the applied extrinsic electric field (max ±127 kV/cm) resulting in an asymmetric effective electric field.
Due to this superposition of the two electric fields the effective electric field is higher in the direction towards the bottom interface than towards the top surface.
As a consequence, higher strains are observed for negative voltages compared to positive voltages leading to asymmetries in the measured butterfly curves (see Fig. 3(c)).
While the effective field for negative applied voltages is sufficient to polarize the film in one direction, it is not clear if the magnitude of the effective electric field for positive applied voltages is large enough to overcome the positive coercive field Ec (+40 kV/cm and −14 kV/cm) and thus to switch the polarization of the studied film [29]. Further experiments are needed to uncover the origin of this behavior.