Ferroelectrics at the nanoscale

Abstract

There are several factors which make the investigation and understanding of nanoscale ferroelectrics particularly timely and important. Firstly, there is a market pressure, primarily from the electronics industry, to integrate ferroelectrics into devices with progressive decreases in size and increases in morphological complexity. This is perhaps best illustrated through the roadmaps for product development in FeRAM (Ferroelectric Random Access Memory) where the need for increases in bit density will require a move from 2D planar capacitor structures to 3D trenched capacitors in the next few years. Secondly, there is opportunity for novel exploration, as it is only relatively recently that developments in thin film growth of complex oxides, self‐assembly techniques and high‐resolution ‘top–down’ patterning have converged to allow the fabrication of isolated and well‐defined ferroelectric nanoshapes, the properties of which are not known. Thirdly, there is an expectation that the behaviour of small scale ferroelectrics will be different from bulk, as this group of functional materials is highly sensitive to boundary/surface conditions, which are expected to dominate the overall response when sizes are reduced into the nanoscale regime.This feature article attempts to introduce some of the current areas of discovery and debate surrounding studies on ferroelectrics at the nanoscale. The focus is directed primarily at the search for novel size‐related properties and behaviour which are not necessarily observed in bulk. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ferroelectric nanoparticles, wires and tubes: synthesis, characterisation and applications

“…The on-going dimensional downscaling of materials, to cram more components onto integrated circuits, in turn gives a great boost to the evolution of potential nanostructured ferroelectric materials and devices. [12][13][14][15][16][17][18][19][20][21] For instance, memory 40 storage based on ferroelectric polarisation reversal has been predicted as one of the emerging memory technologies 12 , owing to their high read-write speed, low power consumption and long rewriting endurance. 27,28 Size and dimensionality plays a critical role in determining the 45 ferroelectric characteristics of a material at the nanoscale, due to the different ways in which dipoles align in ferroelectric crystals.…”

“…These changes could alter some of the ferroelectric functionality, such as phase transition temperature or Curie temperature (TC), domain dynamics, dielectric constant, coercive field, or spontaneous polarisation, piezoelectric response, etc., at 55 the nanoscale. 14,21,[29][30][31][32][33][34][35] In short, low dimensional ferroelectrics show marked deviations in their properties compared to their bulk ferroelectric counterparts, mostly due to the great enhancement of surface area. Since the surface characteristics of nanostructures are morphology and size dependent, the type of nanostructuring 60 used in ferroelectrics must be based on the dependence of some parameter related to the ferroelectric functionality under consideration.…”

Structural Transitions of Silicate Nanocrystals in the Glass

“…For example, the Curie temperature T C for nanostructured ferroelectrics decreases with the size d of nanocrystals as d -1 , with it's lowest value reaching T c ≈ 300 K at d ≈ 3 nm ( fig. 3 in [1]). The size of nanocrystals in these investigations was defined as the diameter of nanowire, i.e.…”

Effects of Elastic Coupling between BaTiO3 Ferroelectric Film and a Substrate with Finite Thickness on Piezoelectric Coefficients

“…Different from corresponding bulk materials, many film heterostructures have complex geometries in microdevices which require using numerical analysis methods to evaluate performance, but it is difficult to be undertaken * corresponding author; e-mail: chanway@njupt.edu.cn for such analyses without comprehensive understanding of the full set of properties of the films. These considerations have promoted to understand the piezoelectric performances of the film heterostructures [8][9][10][11]. Lefki and Dormans proposed two methods for treating a ferroelectric film [12].…”