Piezoelectric properties in sub-micron ferroelectric polymer films

The piezoelectric and electrostrictive response of spun cast films of the ferroelectric vinylidene fluoride/trifluoroethylene copolymers, with thicknesses around 100 nm, have been measured. The measurements have been carried out both on a macroscopic scale, using interferometry, and on a microscopic scale using atomic force microscopy. The interferometry results suggest that in samples exposed to a constant external electric field, the biased electrostrictive response causes a significant decrease in the apparent piezoelectric response. The atomic force microscope results allow the observation of electromechanical activity at the scale of the individual crystallites. Preliminary results from unpoled films suggest that the electrostrictive response is largest in the region at the interface of the crystalline and amorphous phases. A small piezoelectric response is also observed in this region, possibly arising from biased electrostriction.