Local polarization switching in stressed ferroelectric polymers

Ferroelectric polymers are used in flexible organic ferroelectric memories, ferroelectric polarization enhanced organic solar cells, and organic multiferroics. Therefore, understanding their polarization switching mechanism under bending is important for the operation of such devices. Here, we study locally by piezoresponse force microscopy (PFM) polarization switching in bent thin films of the ferroelectric polymer poly(vinylidene fluoride-ran-trifluoroethylene). In bent samples, higher probability of domain nucleation, faster domain wall propagation, and lower coercive field are consistently observed by PFM. We ascribe these observations to a decrease of the domain wall pinning energy, resulting from the mechanical energy stored in the sample due to bending in the presence of the compression gradient generated below the PFM tip.