Ferroelectricity and negative piezoelectric coefficient in orthorhombic phase pure ZrO2 thin films

A new approach for epitaxial stabilisation of ferroelectric orthorhombic (o-) ZrO2 films with negative piezoelectric coefficient in ∼ 8nm thick grown by ion-beam sputtering is demonstrated. Films on (011)-Nb:SrTiO3 gave the oriented o-phase, as confirmed transmission electron microscopy and backscatter diffraction mapping, grazing incidence x-ray Raman spectroscopy. Scanning probe techniques macroscopic polarization-electric field hysteresis loops show behavior, saturation polarization ∼14.3 µC/cm2, remnant ∼9.3 µC/cm2 coercive ∼1.2 MV/cm. In contrast to o-films (011)-Nb:SrTiO3, (001)-Nb:SrTiO3 showed mixed monoclinic (m-) o-phases causing an inferior ∼4.8 over 50% lower than one observed film (011)-Nb:SrTiO3. Density functional theory (DFT) calculations SrTiO3/ZrO2 interfaces support experimental findings a stable polar o-phase growth (011) Nb:SrTiO3, they also explain coefficient.