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 piezore-A C H T U N G T R E N N U N G sponse 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 [*] Dr.Figure 4. a, b) Top: Large-area and small-area AFM images along with corresponding thickness profiles from the deposits of samples A (a) and B (b), respectively. The hysteretic piezoresponse versus bias voltage curves from the samples are shown in the corresponding bottom panels, while the changes in phase angle with voltage are shown in the insets.

Scale effects and the formation of polarization vortices in tetragonal ferroelectrics

“…The wire is assumed to extend indefinitely out of the model plane, such that plane strain and plane electric field conditions apply. Minimum cross-sectional widths of 20nm were considered, noting that ferroelectricity has been observed in BaTiO3 structures from a few nanometers in size upwards [34][35][36]. The wire is assumed to be simply supported, with traction free surfaces.…”

Macroscopic ferroelectricity and piezoelectricity in nanostructured BiScO3–PbTiO3 ceramics

“…4 The feasibility of these ferroelectric ceramic based, miniaturized technologies depends on the scaling of the macroscopic functional properties with size. 8 However, this does not guarantee the functionality of the ferroelectric ceramic nanostructured elements that depends on how macroscopic properties such as polarization switching and retain, linear polarizability, and piezoelectricity scale with the decrease in grain size. 5 There are now solid evidences that ferroelectricity persists in nanoscale films, 6 wires, 7 and particles.…”

Relaxor Behavior, Polarization Buildup, and Switching in Nanostructured 0.92 PbZn1/3Nb2/3O3–0.08 PbTiO3 Ceramics

“…Ferroelectricity is a cooperative phenomenon, and it was long thought that a minimum volume was necessary to sustain the spontaneous polarization; this raises the existence of a fundamental size limit below which ferroelectricity vanishes 11. 12 First‐principles calculations and experimental studies on nanostructured films,13–16 wires,17, 18 particles,19, 20 and ceramics21 have shown that ferroelectricity persists at the nanoscale and thus, that the downscaling of ferroelectric‐based piezoelectric technologies is feasible. However, most studies focused on prototype, simple perovskites, such as BaTiO 3 , PbTiO 3 , or tetragonal Pb(Zr,Ti)O 3 , whereas results on high‐piezoelectric‐coefficient morphotropic‐phase‐boundary (MPB) materials are scarce 22.…”