The report aims to show how in-situ diffraction experiments with synchrotron light contribute in the coherent picture of structural evolution at different length and time scales. As characteristic examples taken from experiments done at BM01 beamline at ESRF, we disucss the symmetry aspects of PMN-PT and PIN-PMN-PT near morphotropic compositions, lack of inversion symmetry in methil-amonnia lead iodide, manipilation with domain structure of ferro- and anti-ferroelectrics with electric field and temperature.

Lead zirconate titanate [Pb(Zr, Ti)O3; PZT)] films have been widely used for piezoelectric MEMS applications due to their superior piezoelectric properties. The piezoelectric response of PZT can be classified into intrinsic factors due to lattice deformation and extrinsic factors due to changes in the domain structure caused by the application of an electric field. Understanding these factors has been carried out not only by electrical properties, but also by in-situ measurements of XRD and Raman spectroscopy under an applied electric field. These measurements for (100)/(001)-oriented tetragonal films suggest the out-of-plane lattice shrinkage of the (100)-oriented domains . It is necessary to understand the effect of out-of-plane lattice shrinkage on the overall piezoelectric response to enhance piezoelectric properties in multidomain films. In this study, we investigated the lattice deformation and domain motion by in-situ XRD under an applied an electric field for (100)/(001)-oriented tetragonal PZT films with various film thicknesses, domain volume fractions, and in-plane orientations. Reversible domain switching from (001) to (100) orientations was observed in epitaxial films with thicknesses of 400-2000 nm and (001)-oriented domain volume fractions of 20-50%. There was negligible elongation of the (001)-oriented domains, while out-of-plane lattice shrinkage of the (100)-oriented domains was mainly observed. Furthermore, this shrinkage was found to increase almost linearly with increasing the (001)-oriented domain volume fractions. As a result, the contribution of the domain switching to the overall piezoelectric response was estimated to be exceed 100%.

Understanding the mechanisms underlying a stable polarization at the surface of ferroelectric thin films is of particular importance both from a fundamental point of view and to achieve control of the surface polarization itself. Uncompensated charges at the surface of a ferroelectric material are responsible for its chemical reactivity and can influence the polarization itself. Therefore, revealing the polarization at (and near) the surface of a ferroelectric material is important not only from a fundamental point of view, but also to obtain a deeper insight into its surface chemistry and learn how to exploit it for technologically relevant catalytic reactions. Different from X-ray diffraction, the X-ray standing wave (XSW) technique can probe the average polarization of a crystal. In this study, we demonstrate that the XSW technique even allows the surface polarization profile of a ferroelectric thin film to be probed directly. The samples under study are three differently strained BaTiO3 thin films grown on scandate substrates, with a SrRuO3 film as bottom electrode. With picometer accuracy, Ti and Ba atomic positions near the surface are determined, giving direct access to the local ferroelectric polarization at and below the surface. By employing X-ray photoelectron spectroscopy, a detailed overview of the oxygen-containing species adsorbed on the surface, upon exposure to ambient conditions, is obtained. The combination of structural and spectroscopic information allows us to conclude on the most plausible mechanisms that stabilize the surface polarization in the three samples under study. The different amplitude and orientation of the local ferroelectric polarizations are associated with surface charges attributed to the type, amount and spatial distribution of the oxygen-containing adsorbates.

Ferroelectric materials are widely used in modern electronic devices, from capacitors to data storage, sensors, transducers, and sound emitters.
These materials exhibit a spontaneous and switchable electric polarization that arises from a non-centrosymmetric arrangement of positively and negatively charged atoms within the crystal structure which leads to a permanent electric dipole. A wide range of different components can be applied ranging from classic components like metal-oxides in a perovskite structure such as barium titanate or lead zirconate titanate or soft polymers like PVDF. In this talk, we provide an overview and introduction of three different modes of piezo force microscopy: Off-resonance single frequency PFM, resonance-enhanced single frequency PFM and dual frequency resonance tracking (DFRT) PFM. We briefly discuss the advantages and disadvantages of these modes and demonstrate how they can be combined with a force-distance-curve-based mode to avoid lateral shear force and enable destruction-free imaging of various material properties such as the adhesion and stiffness as well as the piezo-/ferroelectricity on a local scale. Finally, we provide an outlook on how such investigations can be combined with other modes of the broad family of Atomic Force Microscopy like Kelvin Probe Force microscopy by characterizing and switching ferroelectric domains in hBN/graphene 2D heterostructures. Accordingly, we present the versatility of AFM-based techniques to provide a comprehensive analytical toolbox for a large variety of samples.