Imprint in Poly(vinylidenefluoride-trifluoroethylene)

Abstract

Imprint effects are studied in Poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) metal-ferroelectric-metal (MFM)-capacitors. Imprint refers to a degradation mechanism in ferroelectrics which is found to take place on a logarithmic time scale. We present that the displacement of the polarization hysteresis loop along the voltage axis, the switching time, the polarization and the capacitance altogether change linearly as a function of the logarithm of time elapsed after poling. This suggests that these can be denoted as direct or indirect imprint effects. Furthermore by normalizing the capacitance and the coercive voltage, all values were found to change independently of thickness. This indicates that imprint is caused by mechanisms in the bulk. In a second experimental section we present that the two frequently used models to explain imprint in P(VDF-TrFE), i.e. the space charge model and the dead layer model are not consistent with our experimental findings.