Table 1 BTO and SRO layer thicknesses, \(t_\textrm{BTO}\) and \(t_\textrm{SRO}\), resulting from grazing X-ray reflectivity (see “Methods”, “Grazing X-ray reflectivity” and Supplementary Fig. 1). All substrates are 0.5 mm thick. The root mean square surface roughness \(S_\textrm{RMS}\) of BTO thin films was determined from AFM images of \(3.9\times 3.9\,\upmu \hbox {m}^2\) area. Compressive in-plane strain in BTO (\(\varepsilon ^{a}_\textrm{BTO}\)) thin films, measured by X-ray reciprocal space maps (Fig. 2a–c). Orientation of the average BTO polarization \(\textrm{P}\) measured by PFM (Fig. 2d–f).

From: Surface polarization profile of ferroelectric thin films probed by X-ray standing waves and photoelectron spectroscopy