Orientation engineering is a universal strategy for ferroelectric trans-switching

Abstract

About two decades ago, ``strain engineering'' emerged as a powerful strategy to tune epitaxial thin films. Here we contend that ''orientation engineering'' - that is, controlling the film's growth direction - constitutes a complementary design route that opens unprecedented opportunities and deserves greater attention. Specifically, we show that orientation engineering can endow standard ferroelectric compounds with exotic and useful behaviors that may be difficult or impossible to obtain otherwise. Critically, we predict it readily enables ''trans-switching,'' where polarization components switch perpendicularly to the applied electric field, paving the way for novel 3D device architectures. We also show that, by controlling the electric screening provided by electrodes in contact with the film, ferrielectric behavior can be obtained. Notably, one can even design an operational mode where the switching is, in effect, fully transversal to the applied field. Supported by phenomenological calculations for representative compounds LiNbO$_3$ and BaTiO$_3$, we thus propose orientation engineering as a powerful and general method to unlock unprecedented functionalities in common ferroelectrics.