Direct Observation of Ferroelectricity in Quasi‐Zero‐Dimensional Barium Titanate Nanoparticles

Abstract

Understanding the behavior of ferroelectric response in zero-dimensional systems, that is, under three-dimensional quantum confinement, is an important task from the technological point of view, which might lead to further miniaturization of electrical devices. Evidently, carrying out direct electrical measurements on ideal zero-dimensional nanoparticles is an extremely nontrivial process, although several experimental reports employing indirect methods have been published. However, the use of recently developed piezoreA force microscopy (PFM) techniques, in conjunction with the careful choice of substrates and appropriate preparation of samples for measurements, makes it possible to experimentally observe this phenomenon on nearly ideal dimensionless systems. Ferroelectric (FE) systems belong to an extremely important class of materials because of the possibility of utilizing them for fabricating ferroelectric random access memories (FERAMs) and microelectromechanical systems (MEMS), which stem from their associated pyro-, piezo-, and ferroelectric properties. In comparison with bulk ferroelectric materials, lower-dimensional structures promise to increase the efficiency of such devices to a large extent and, therefore, future development of the electronics industry strongly requires a clear understanding of the relationship between properties and particle sizes. The key question is whether the ferroelectric phase transitions and multistable states still exist in lower dimensions or not. Previous theoretical studies [1] predicted that polarization values should be smaller in two dimensions (thin films) and below a certain