Giant Dielectric Permittivity in Ferroelectric Thin Films: Domain Wall Ping Pong.

An Quan Jiang,James F Scott,Min Hyuk Park,Sijung Yoo,Yu Jin Kim,David Wei Zhang,Xiang Jian Meng,Cheol Seong Hwang

doi:10.1038/srep14618

Abstract

The dielectric permittivity in ferroelectric thin films is generally orders of magnitude smaller than in their bulk. Here, we discover a way of increasing dielectric constants in ferroelectric thin films by ca. 500% by synchronizing the pulsed switching fields with the intrinsic switching time (nucleation of domain plus forward growth from cathode to anode). In a 170-nm lead zirconate titanate thin film with an average grain size of 850 nm this produces a dielectric constant of 8200 with the maximum nucleus density of 3.8 μm−2, which is one to three orders of magnitude higher than in other dielectric thin films. This permits smaller capacitors in memory devices and is a step forward in making ferroelectric domain-engineered nano-electronics.

Highlights

Classic ferroelectric oxide films provide large ionic displacements of individual atoms down to the atomic layer thickness, for example, ~2.4 nm for SrRuO3/BaTiO3/SrRuO3 sandwiches, and the related functionalities in these devices can be achieved in the ns-ps time scale as their physical dimensions shrink down into the nanometer scale[2,3,4,5,6]
This huge dielectric response arising from the domain oscillation can occur at temperatures below the compositional and mesostructural heterogeneities near phase transition (Curie) point, which is completely different from the large enhancement in dielectric constant near the ferroelectric-paraelectric phase transition of several ferroelectric materials, such as the epitaxial (Ba,Sr)TiO3 thin films[21]
In BaTiO3 single crystals with hetero-valence impurities a large nonlinear electrostriction is generated during 90° domain switching[22]; a restoring force arises from temporarily uncompensated charged defects

Summary

Introduction

Classic ferroelectric oxide films provide large ionic displacements of individual atoms down to the atomic layer thickness, for example, ~2.4 nm for SrRuO3/BaTiO3/SrRuO3 sandwiches, and the related functionalities in these devices can be achieved in the ns-ps time scale as their physical dimensions shrink down into the nanometer scale[2,3,4,5,6]. The experimental value of the dielectric constant is always much smaller than the expected value (ε = dPf/ε 0dEf, where ε0 is the vacuum permittivity) because much of the polarization charge does not follow the small oscillating AC field These effects have severely hampered the applications of ferroelectrics to memory devices, miniaturized sensors, actuators, phase shift antenna arrays, and energy harvesting systems[7,8]. In the present study these early ideas are extended to the longitudinal oscillation of domains that do not quite extend from a cathode to an anode This huge dielectric response arising from the domain oscillation can occur at temperatures below the Curie point, which is completely different from the large enhancement in dielectric constant near the ferroelectric-paraelectric phase transition of several ferroelectric materials, such as the epitaxial (Ba,Sr)TiO3 thin films[21]

Methods

Results

Conclusion