Studies of dielectric and switching characteristics in VDF/TrFE copolymer thin films by means of pulse-train measurements

The polarization reversal of ferroelectric material proceeds through the nucleation and growth process of reversed domains. In order to study the polarization reversal process in the VDF/TrFE thin films, we applied a train of short voltage pulses (t_on=0.2μs ∼50μs) to the sample and measured the charge response as a function of time. The switching time τs becomes longer as the pulse length ton becomes shorter. Even when we applied a very short pulse t_on=0.2μs with which almost no polarization reversal proceeds at the early process, the polarization reversal eventually occurs. Removing the dielectric contribution from the observed charge response extracts the time evolution of intrinsic ferroelectric component. It clearly demonstrates the transition from the nucleation process to the growth process during polarization reversal. We will discuss the kinetic process of polarization reversal with a model based on the results of the pulse-train method.