Surface Pyroelectricity and Piezoelectricity of Centrosymmetric Crystals

Properties of surfaces often define functionalities and applications of a large variety of materials, e. g., epitaxial growth of thin films, catalytic and optical properties. For this reason, advances in techniques for surface characterization are of great importance. Here we present an overview of the work conducted together with Prof. Meir Lahav over the last decade to detect and quantify near surface polar layers (NSPL). Though thin, these layers may accumulate considerable polarization and, thereby, affect surface properties. We demonstrated that pyroelectric measurement carried out with periodic temperature change protocol (modified Chynoweth) might be a primary tool to study NSPL. Two fundamentally different examples are considered. (i) NSPL in α-glycine crystals develops as a result of solvent incorporation, e. g., water. This layer is maybe tens or even hundreds of micrometers thick, sometimes, thick enough to allow piezoelectric measurements. (ii) NSPL in SrTiO₃ results from surface relaxation and it is only a few Angstroms thick. Nevertheless, NSPL in SrTiO₃ has a polarization comparable with strongly ferroelectric materials, tens of μC/cm².