Effect of thermal annealing on ferroelectric domain structures in poly(vinylidene-fluoride-trifluorethylene) Langmuir-Blodgett thin films

We report a piezo-response force microscopy study of the effect of thermal annealing on ferroelectric domain structures in 6 to 20 monolayer (11 to 36 nm) polycrystalline poly(vinylidene-fluoride-trifluorethylene) thin films prepared using the Langmuir-Blodgett approach. Stripe-shape domains have been created at room temperature and subjected to thermal annealing at progressively higher temperatures up to the ferroelectric Curie temperature TC of approximately 110 °C. The static configuration of the domain walls exhibits no appreciable temperature dependence after thermal annealing, with the domain-wall roughness exponent ζ ranging from 0.4 to 0.5. Above 80 °C, we observed spontaneous polarization reversal at randomly scattered local sites in both polarization states. The number of domain nucleation centers increases rapidly as a function of temperature. We compared the thermally driven domain formation in ferroelectric polymers with those observed in ferroelectric oxides and attributed the difference to ...