Evolution of flux-closure domain arrays in oxide multilayers with misfit strain

Abstract

Ferroelectric flux-closure domains have attracted great attention due to their potentials in high density data storage. For their future applications, it is important to understand their evolution with different factors, such as misfit strain. In this work, a flux-closure domain consisting of a vertical 180° domain wall with two symmetric a domains in both ends (“I” type closure) was observed in nearly unstrained SrTiO3/PbTiO3 multilayers by aberration corrected Transmission Electron Microscopy, which was speculated to be mainly induced by the strong depolarization field near the interface. With the tensile strain increasing, the small a domains in “I” type flux-closures grow gradually and eventually change to the well-known “V” type flux-closures. On the basis of a combination of experimental results and phase field simulations, the phase diagram of the stabilized domain arrays versus the strains in PbTiO3 films are established. These results provide significant information on understanding the formation mechanism of flux-closure domains and shed light on their controlled growth. In addition, it paves a way to reduce the economic cost in their commercial applications because the SrTiO3 substrate is easy to synthesize and much cheaper than scandate substrates.