Chapter 1 - Introduction

Abstract

In this chapter, I will begin with a discussion of the general design methodology for a thin film heterostructure, then follow up by introducing several important nanostructures in a ferroelectric (FE) thin film, which should be paid the uttermost attention during the design phase of a FE thin film–based device. These nanostructures include interfaces, grains and grain boundaries, FE and ferroelastic domains, and different phases/phase boundaries. They deviate from a homogeneous lattice structure of a FE and hence can also be called nanostructural inhomogeneities with respect to a FE single-domain single crystal. These nanostructures play important and even dominant roles in determining the functional properties of a FE film. To elaborate on this structure–property relationship a brief introduction of ferroelectricity via the case study of a perovskite “displacive ferroelectric” is made, and a spontaneous electric polarization with bistable states as the foundation of ferroelectricity is illustrated. Next, the very intuitive technological application in memories for FE materials is introduced, followed by other polarization-derived material properties that can be utilized in the applications for energy harvesting, conversion, and storage. Then the intrinsic properties due to lattice effects and extrinsic properties due to the aforementioned structural inhomogeneities in FEs are discussed. The extrinsic properties often dominate in FEs, and their optimizations can be achieved in FE films by engineering of the related nanostructures, that is, nanodomains, nanograins, nanophases, and nanoscale interfaces. Lastly, the methods of strain engineering and interface engineering for these nanostructures are discussed, with a list of techniques summarized from the literature. This introduction of the book ends with a brief description of the contributing chapters.