Critical size in ferroelectric nanostructures

Recently, several attempts have been made to determine the critical size in ferroelectricity. Due to the development of ferroelectric nanostructure technology, this fundamental problem had also become crucial for applied research. It is shown that although the theory predicts the existence of a finite critical size, ferroelectric polarization and its switching can be observed in monolayer films, at least in the case of ferroelectric vinylidene fluoride-trifluoroethylene copolymer P[VDF-TrFE] films prepared by the Langmuir-Blodgett method. The experimental search for the critical size in perovskite ferroelectrics is briefly reviewed. It is shown that the Landau-Ginzburg theory predicts the critical size to be infinitely small if the extrinsic effect of the film-electrode strain mismatch is taken into account. Special features of the switching dynamics of ultrathin ferroelectric films are also considered.