Electric-field-controlled directional motion of ferroelectric domain walls in multiferroic BiFeO3 films

We describe the directional ferroelectric domain wall motion in a multiferroic BiFeO3 thin film, which was grown epitaxially on a vicinal (001) SrTiO3 substrate. A structural analysis of the film shows that a strain gradient is developed in our film, which creates a symmetry breaking in a ferroelectric double-well potential. The asymmetric double-well potential can cause ferroelectric domain walls to move sideways with preferred directionality under a vertical electric field. Our results suggest the possibility of controlling the direction of domain growth with an electric field by imposing constraints on ferroelectric films, such as a strain gradient.