Interface effect on polarization switching and critical thickness of crystallization in P(VDF-TRFE) copolymer thin films

In poly(vinylidene fluoride-trifluoroethylene) copolymer spin cast films, it has been observed that the polarization switching time increases as the film thickness is reduced. We will show that this change with thickness can be divided into two thickness regimes, those above a critical thickness and below this critical thickness. For films above the critical thickness, the change is in the switching behavior is mainly due to interface effect. While for films below the critical thickness, there is an additional and very large increase of the switching time with reduced film thickness, which is caused by a large drop of the crystallinity in this thickness range. It has been observed that this critical thickness, below which the crystallization in the polymer films is strongly hindered, depends on the film annealing conditions and is directly related to the thermodynamic stable crystallite thickness.