Surface polarization profile of ferroelectric thin films probed by X-ray standing waves

BaTiO₃ is a prototypical ferroelectric material with spontaneous polarization associated with atomic displacements. This polarization results in the accumulation of charges at the surface which needs to be compensated to stabilize the bulk polarization state. One of these charge compensation mechanism is the presence of surface adsorbates. In this study, we employ the X-ray standing wave technique to probe atomic positions within the unit cells near the surface and thus deduce the surface polarization profile in ferroelectric thin films combining structural and spectroscopic information.