Intrinsic flexoelectricity of van der Waals epitaxial thin films

The direct measurement of flexoelectric coefficients in epitaxial thin films is an unresolved problem, due to the clamping effect substrates which induces a net strain (and hence parasitic piezoelectricity) addition gradients and flexoelectricity. Herein, we propose demonstrate use van der Waals epitaxy as successful strategy for measuring intrinsic (clamping-free = films. We have made, measured, compared ${\mathrm{BaTiO}}_{3}$ ${\mathrm{SrTiO}}_{3}$ film capacitor heterostructures grown both by conventional oxide-on-oxide oxide-on-mica epitaxy, found that, whereas former dominated piezoelectricity, response latter truly flexoelectric. results are backed theoretical calculations film-substrate mechanical interaction, well measurements that confirm strain-free state thus emerges powerful new tool study flexoelectricity and, particular, they finally allow exploring phenomena at nanoscale (where highest) with experimental knowledge actual