Mechanical switching of ferroelectric polarization in ultrathin BaTiO3 films: The effects of epitaxial strain

Electrical switching of spontaneous polarizations has been intensively studied for decades in ferroelectric thin films for non-volatile memory applications. Recent advances have shown that the polarization in ultrathin ferroelectric films can also be switched by a mechanical loading force owing to the flexoelectric effect. In this work, we report the strain effects on the mechanical switching in 12-unit-cell-thick BaTiO3 ultrathin films grown coherently on SrRuO3-buffered SrTiO3, DyScO3, and GdScO3 substrates. The mechanical threshold for polarization reversal increases with increasing in-plane compressive strain, associated with the increased coercive field for electrical polarization switching. These are ascribed to the increase of switching barrier in BaTiO3 thin films as the compressive strain increases. (C) 2014 AIP Publishing LLC.