Characterization of domain walls in BaTiO3 using simultaneous atomic force and piezo response force microscopy

Abstract

In this letter a method to simultaneously measure the physical and the polarization thickness of a 90°d omain wall in a ferroelectric perovskite is presented. This method combines accurate atomic force microscopy and piezoresponse force microscopy scans of the same area with little drift and an analysis of the entire scanned area. It is found that the physical thickness is significantly narrower ͑about seven and a half times͒ than the polarization thickness in a 90°domain wall in BaTiO 3 . Evidence of the trapping of defects at such domain walls is also found. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2185640͔ Ferroelectric materials offer great potential for next generation high density storage devices, such as nonvolatile random memory access and high strain actuators in microelectromechanical systems applications due to their inherent high dielectric properties and high strain response. 1-3 Their macroscopic response to mechanical, electrical and optical loads is strongly related to their microstructural domain patterns. 4,5 The formations and kinetics of these domains are governed by the underlying atomistic structure, and their interaction with domain walls and material imperfections. As the size of the devices reduces to micro-and nano-scale, the motion and interaction of twin ͑domain͒ walls significantly influences the overall piezoelectric, optical, and mechanical response of the device. 6 In order to predict and control the phenomenological behavior of twin wall kinetics, their physical and electrical properties need to be accurately determined.Many of the current experimental techniques, including x-ray diffraction and high-resolution transmission electron microscopy ͑TEM͒ are capable of imaging domain walls, but are often unable to provide information about their polarization. 7,8 Also, since these techniques are based on diffraction principles, they only provide averaged information about the physical twin wall thickness. 9 Current far field techniques are limited in their resolution by the wavelength of the light and, although near-field techniques such as NSOM provide useful information, they are still difficult to use.An experimental approach for determining the physical and electrical twin wall thickness in a ferroelectric perovskite material BaTiO 3 by simultaneously using a combination of atomic force microscopy ͑AFM͒ and piezoresponse force microscopy ͑PFM͒ is described here. The recorded AFM and PFM images are quantitatively compared to their respective displacement and polarization fields using the widely used and accepted Devonshire-Ginzburg-Landau ͑DGL͒ phenomenological model. [10][11][12] As has been shown by Shilo, Ravichandran, and Bhattacharya 9 for the case of PbTiO 3 , fitting the measured AFM displacement field to the DGL model by means of a least-squares method produces excellent results with nanometer resolution. Here, this approach is extended to include PFM measurements to determine the polarization domain wall thickness simultaneously along with the physical domain ...

Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

“…4, where in steady state, the dopants segregate along a domain wall in an asymmetric manner creating a defect dipole. Recent simultaneous AFM-PFM measurements of emerging 90 domain walls in BaTiO 3 show that the physical width is significantly smaller (over 7 times) than the piezoelectric width consistent with longrange electrostatic interactions [21]. Further, the decoration of the domain wall with defects is consistent with experimental observations of Shilo et al [22] and provides a mechanism for the domain wall to have a memory of its location during annealing.…”

Piezoelectric response hysteresis in the presence of ferroelastic 90° domain walls

“…[5][6][7][8][9] This is one of the main reasons, which together with the clamping effect of the substrate, 10,11 is used to explain the often reported immobility or low mobility of twins in ferroelectric films. In agreement with the analysis of Ishibashi, Franck et al 18 found that the polarization width of a 90°domain wall is much thicker ͑about 7.5 times͒ than the physical width, which was estimated to be 10 nm. 13 In the past few years, several publications were dedicated to theoretical and experimental investigations of atomistic structure [14][15][16] and polarization reversal processes 17,18 of 90°domain walls.…”

“…25 Therefore, it is reasonable to attribute the enhancement of the piezoelectric coefficient shown through the largest d 33 -V curve in Fig. 16,18,27 In summary, a spatial variation of the d 33 piezoelectric coefficient measured on ferroelectric capacitors was observed for PZT films possessing a c / a / c domain structure. The inset in Fig.…”

A model for large electrostrictive actuation in ferroelectric single crystals

“…(3). Different domains (having different state P and e) are separated by very narrow domain walls (Shilo et al, 2004;Franck et al, 2006) in which P and e gradually change from one preferred state to another.…”