Pixcel detector

The crystalline state was determined by X-ray diffraction (XRD) by using a X’Pert Pro MPD powder X-ray diffractometer with a PIXcel detector (Panalytical, Germany) and a CoKα radiation source (λ = 1.54187 Å). Samples were measured to CoKα radiation (40 kV, 35 mA) at a scanning rate of 2.4°/min between 10 and 70° 2θ with a step size of 0.039° 2θ. To enhance the viscosity of the liquid suspensions, prior the measurements, locust beam gum (3% (w/w)) was added to the aqueous suspensions. This was done to avoid the need for drying of the samples prior to analysis, which in turn could induce crystallization or crystal growth and thus lead to changes in the crystalline structure of the original suspensions [27 (link)].

To probe the evolution of surface morphology, PbZr_0.2Ti_0.8O₃ (tetragonal, a = 3.95 Å and c = 4.13 Å)43 films of thickness 25–150 nm were grown on 25 nm SrRuO₃/SrTiO₃ (001) (cubic, a = 3.905 Å) substrates using pulsed-laser deposition. SrRuO₃ was grown at 645 °C in an oxygen pressure of 100 mTorr with a laser fluence of 1.30 J/cm² and frequency of 10 Hz. Subsequently, PbZr_0.2Ti_0.8O₃ was grown at 635 °C in an oxygen pressure of 200 mTorr with a laser fluence of 1.35 J/cm² and frequency of 3 Hz. SrRuO₃ grows coherently strained to the substrate and the difference in lattice parameters of PbZr_0.2Ti_0.8O₃ and SrTiO₃ corresponds to a lattice mismatch of −1.24%. Detailed structural information for the various heterostructures was obtained using high-resolution X-ray diffraction (XPert MRD Pro equipped with a PIXcel detector, Panalytical) including θ–2θ scans and reciprocal space maps (RSMs). Topographic study of the films was carried out using atomic force microscope (AFM) (MFP-3D, Asylum Research). The cross-section, dark-field transmission electron microscopy (TEM) images of the heterostructures were obtained using JEOL 3010 microscope at the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory.

X-ray θ-2θ scans were obtained by high-resolution X-ray diffraction (XPert MRD Pro equipped with a PIXcel detector, Panalytical). The PFM studies were carried out in areas of pre-poled capacitors by a MFP-3D AFM (Asylum Research) using Ir/Pt-coated conductive tips (Nanosensor, PointProbe® Plus Electrostatic Force Microscopy, force constant ≈2.8 N m⁻¹). In order to image the domain structure under the pre-poled capacitors, first we pre-poled multiple capacitors into different polarization states and then coated a layer of inversely patterned photoresist using photolithography that only covers the PbZr_0.2Ti_0.8O₃ film region (Supplementary Fig. 7d). The uncovered top La_0.7Sr_0.3MnO₃ electrodes could be readily etched away using dilute H₃PO₄ acid (dilution ratio 1 part acid:5 parts water) (Supplementary Fig. 7e). The inversely patterned photoresist was left on the film surface serving as a marker that aids the accurate location and imaging for regions that were under the pre-poled capacitors. Here we also provide PFM results of four states discussed in Fig. 4 that were scanned in the entire area of capacitors (Supplementary Fig. 8).