Ferroelectric Domain Imaging Research Articles

Second-harmonic imaging of ferroelectric domains in LiNbO 3 with micron resolution in lateral and axial directions

Second-harmonic imaging of ferroelectric domains in LiNbO 3 with micron resolution in lateral and axial directions

Nondestructive imaging and characterization of ferroelectric domains in periodically poled crystals

We report the nondestructive investigation and visualization of periodically poled domains in ferroelectric potassium titanyl phosphate (KTP) crystals using polarization sensitive scanning force microscopy (SFM). Applying an alternating voltage technique to SFM allows ferroelectric domain wall resolution beyond 100 nm. Image contrast between KTP and Rb doped KTP, i.e., rubidium titanyl phosphate (RTP) regions arises from the differential piezoelectric response. We find the polarization vectors in both KTP and RTP to be aligned parallel to the negative z axes as deduced (a) when comparing our data with a ferroelectric reference sample, i.e., tri-glycine sulfate (b) from comparison of nanoscale hysteresis loops recorded on KTP and RTP, and (c) from direct domain switching in KTP applying very high electric fields between tip and counter electrode. The latter experiments show that nanoscale ferroelectric domains in KTP switch from the negative to the positive z-axes alignment for electric fields stronger than 750 V/cm. Nevertheless, spontaneous backswitching is observed after a couple of minutes.

Control and imaging of ferroelectric domains over large areas with nanometer resolution in atomically smooth epitaxial Pb(Zr0.2Ti0.8)O3 thin films

We have investigated the possibility afforded by epitaxial ferroelectric oxide thin films to control and image locally the polarization field of ferroelectrics over large areas with submicron resolution, using the metallic tip of an atomic force microscope as a mobile top electrode and local probe of the ferroelectric properties. Atomically smooth films of Pb(Zr0.2Ti0.8)O3, showing a root-mean-square roughness of typically a few angstroms, could be uniformly polarized and imaged over areas as large as 2500 μm2 without introducing any topographic disorder. Regular arrays of 100 nm wide lines and circular domains with a diameter less than 100 nm were written in arbitrary areas of the uniformly polarized regions.

Scanning force microscopy of domain structure in ferroelectric thin films: imaging and control

Scanning force microscopy (SFM) has been used to perform nanoscale studies of domain structures and switching behaviour of (PZT) thin films. An SFM piezoresponse mode, based on the detection of the piezoelectric vibration of a ferroelectric sample, was shown to be suitable for high resolution imaging of ferroelectric domains in thin films. The lower limit of the piezoresponse mode imaging resolution depends on the radius of the probing tip and is estimated to be of the order of several nanometers. The effect of the film microstructure on the imaging resolution is discussed. The ability of effective control of domains as small as 50 nm by means of SFM has been demonstrated. It is shown that SFM can be used in the investigation of electrical degradation effects in ferroelectric thin films. Formation of regions with unswitchable polarization as a result of fatigue, within grains of submicron size, was experimentally observed.

Nondestructive Imaging of Dielectric-Constant Profiles and Ferroelectric Domains with a Scanning-Tip Microwave Near-Field Microscope

Variations in dielectric constant and patterns of microwave loss have been imaged in a yttrium-doped LiNbO 3 crystal with periodic ferroelectric domains with the use of a scanning-tip near-field microwave microscope. Periodic profiles of dielectric constant and images of ferroelectric domain boundaries were observed at submicrometer resolution. The combination of these images showed a growth-instability–induced defect of periodic domain structure. Evidence of a lattice-edge dislocation has also been observed through a stress-induced variation in dielectric constant.

Atomic resolution imaging of ferroelectric domains

Electron optical principles involved in obtaining atomic resolution images of ferroelectric domains are reviewed, including the methods available to obtain meaningful interpretation and analysis of the image detail in terms of the atomic structures. Recent work is concerned with establishing the relationship between the essentially static chemical nanodomains and the spatial and temporal fluctuations of the nanoscale polar domains present in the relaxor class of materials, including lead scandium tantalate (PST) and lead magnesium niobate (PMN). Correct interpretation of the images required use of Next Nearest Neighbour Ising model simulations for the chemical domain textures upon which we must superimpose the polar domain textures; an introduction to this work is presented. A thorough analysis of the atomic scale chemical inhomogeneities, based upon the HRTEM results, has lead to an improved formulation of the theory of the dielectric response of PMN and PST, which is capable to predict the observed frequency dependence. Thus we now have an imaging tool (HRTEM) which may be combined with solid state and statistical physics principles to provide a deeper understanding of structure/property relationships.

Scanning force microscopy as a tool for nanoscale study of ferroelectric domains

Abstract Scanning force microscopy (SFM) has been used for studying surface morphology of solids for almost ten years. Recently the possibility of ferroelectric domain imaging by SFM was reported. In the present study we exploit SFM for visualization and control of domain structure in ferroelectrics at the nanometer scale. An advanced technique for domain imaging based on the detection of piezoelectric vibration of the ferroelectric sample is presented. The study involves the use of thin films of lead titanate, lead zircon ate titanate and single crystals of barium titanate and lithium niobate. A conductive SFM tip was used to write and image ferroelectric domain patterns with an average resolvable spacing down to 30 nm.

A new holographic technique for the study of antiparallel ferroelectric domains

Abstract Beam-coupling topography is a new, non-destructive holographic technique for spatially resolved imaging of antiparallel ferroelectric domains. Its basic principle is the interference of Bragg-diffracted beams from a holographic grating with collinear, transmitted ones. Full domain contrast and noise suppression is achieved by appropriate control of intensity and phase of the interfering beams. Using Sr0.61Ba0.39Nb2O6.:Ce as an example, it is demonstrated that the method permits spatially resolved measurement of hysteresis loops and monitoring of photoassisted domain switching processes.

Imaging of Ferroelectric Domains in KTiOPO4 Single Crystals by Synchrotron X-RAY Topography

AbstractThe application of synchrotron white beam X-ray topography to the study of ferroelectric domain structures in hydrothermally grown potassium titanyl phosphate (KTiOPO4: KTP) single crystals is reported. The domain walls can be exclusively imaged on topographs with selected diffraction vectors and X-ray wavelengths, while images of other defects, such as dislocations, inclusions and surface scratches, can be simultaneously made very diffuse. The topographic images correspond well with electrostatic toning images. X-ray topography readily reveals the three dimensional shapes of the domain walls. There are two contributions to domain wall contrast: one is fringe-like which can be interpreted in terms of the dynamical theory of X-ray diffraction, and the other is diffuse strain contrast arising from long range strain associated with the wall. These two contributions can be observed simultaneously or separately depending on the diffraction conditions. The long range strain is thought to be associated with the curvature of the domain walls. It appears that the main components of the displacement field associated with this strain are directed approximately perpendicular to the domain wall.

SEM Imaging of Ferroelectric Domains

SEM Imaging of Ferroelectric Domains