Now showing 1 - 10 of 13
  • Publication
    Quantitative determination of tip parameters in piezoresponse force microscopy
    (American Institute of Physics, 2007-05-24) ; ; ;
    One of the key limiting factors in the quantitative interpretation of piezoresponse force microscopy (PFM) is the lack of knowledge on the effective tip geometry. Here the authors derive analytical expressions for a 180 degrees domain wall profile in PFM for the point charge, sphere plane, and disk electrode models of the tip. An approach for the determination of the effective tip parameters from the wall profile is suggested and illustrated for several ferroelectric materials. The calculated tip parameters can be used self-consistently for the interpretation of PFM resolution and spectroscopy data, i.e., linear imaging processes.
    Scopus© Citations 29  434
  • Publication
    Ferroelectric domain wall pinning at a bicrystal grain boundary in bismuth ferrite
    The ferroelectric polarization switching behavior at the 24 degrees (100) tilt grain boundary (GB) in an epitaxial multiferroic BiFeO3 bicrystal film is studied using piezoresponse force microscopy (PFM). The PFM amplitudes across positively and negatively poled GB regions suggest the presence of a frozen polarization component at the interface. The switching experiments demonstrate that the GB attracts the domain wall and acts as a pinning center. The PFM results are compared with conductive atomic force microscopy and spectroscopy, which suggest domain wall pinning at the GB can be partially attributed to increased conductance at the GB.
    Scopus© Citations 67  600
  • Publication
    Spatial distribution of relaxation behavior on the surface of a ferroelectric relaxor in the ergodic phase
    Spatial homogeneity of polarization relaxation behavior on the surface of 0.9Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) crystals in the ergodic relaxor phase is studied using three-dimensional time-resolved spectroscopic piezoresponse force microscopy. The number of statistically independent components in the spectroscopic image is determined using principal component analysis. In the studied measurement time interval, the spectra generally exhibit logarithmic behavior with spatially varying slope and offset, and the statistical distribution of these parameters are studied. The data illustrate the presence of mesoscopic heterogeneity in the dynamics of the relaxation behavior that can be interpreted as spatial variation in local Vogel-Fulcher temperatures.
      433Scopus© Citations 32
  • Publication
    Scanning frequency mixing microscopy of high-frequency transport behavior at electroactive interfaces
    (American Institute of Physics, 2006-04) ; ; ;
    An approach for high-frequency transport imaging, referred to as scanning frequency mixing microscopy (SFMM), is developed. Application of two high-frequency bias signals across an electroactive interface results in a low-frequency component due to interface nonlinearity. The frequency of a mixed signal is chosen within the bandwidth of the optical detector and can be tuned to the cantilever resonances. The SFMM signal is comprised of an intrinsic device contribution and a capacitive mixing contribution, and an approach to distinguish the two is suggested. This technique is illustrated on a model metal-semiconductor interface. The imaging mechanism and surface-tip contrast transfer are discussed. SFMM allows scanning probe microscopy based transport measurements to be extended to higher, ultimately gigahertz, frequency regimes, providing information on voltage derivatives of interface resistance and capacitance, from which device characteristics such as Schottky barrier height, etc., can be estimated. (c) 2006 American Institute of Physics.
      341Scopus© Citations 8
  • Publication
    Electromechanical imaging of biological systems with sub-10 nm resolution
    (American Institute of Physics, 2005-08) ; ; ;
    Electromechanical imaging of tooth dentin and enamel has been performed with sub-10 nm resolution using piezoresponse force microscopy. Characteristic piezoelectric domain size and local protein fiber ordering in dentin have been determined. The shape of a single protein fibril in enamel is visualized in real space and local hysteresis loops are measured. Because of the ubiquitous presence of piezoelectricity in biological systems, this approach is expected to find broad application in high-resolution studies of a wide range of biomaterials. (c) 2005 American Institute of Physics.
    Scopus© Citations 87  424
  • Publication
    Imaging mechanism of piezoresponse force microscopy in capacitor structures
    (American Institute of Physics, 2008-04-18) ; ; ;
    The image formation mechanism in piezoresponse force microscopy (PFM) of capacitor structures is analyzed. We demonstrate that the spatial resolution is a bilinear function of film and top electrode thicknesses and derive the corresponding analytical expressions. For many perovskites, the opposite contributions of d(31) and d(33) components can result in anomalous domain wall profiles. This analysis establishes the applicability limits of PFM for polarization dynamics studies in capacitors and applies them to other structural probes, including focused x-ray studies of capacitor structures. (c) 2008 American Institute of Physics.
      338Scopus© Citations 56
  • Publication
    Vector piezoresponse force microscopy
    (Cambridge University Press, 2006-06) ; ; ;
    A novel approach for nanoscale imaging and characterization of the orientation dependence of electromechanical properties-vector piezoresponse force microscopy (Vector PFM)-is described. The relationship between local electromechanical response, polarization, piezoelectric constants, and crystallographic orientation is analyzed in detail. The image formation mechanism in vector PFM is discussed. Conditions for complete three-dimensional (313) reconstruction of the electromechanical response vector and evaluation of the piezoelectric constants from PFM data are set forth. The developed approach can be applied to crystallographic orientation imaging in piezoelectric materials with a spatial resolution below 10 nm. Several approaches for data representation in 2D-PFM and 3D-PFM are presented. The potential of vector PFM for molecular orientation imaging in macroscopically disordered piezoelectric polymers and biological systems is discussed.
    Scopus© Citations 212  1128
  • Publication
    Nanoelectromechanics of polarization switching in piezoresponse force microscopy
    (American Institute of Physics, 2005-04) ; ; ;
    Nanoscale polarization switching in ferroelectric materials by piezoresponse force microscopy in weak and strong indentation limits is analyzed using exact solutions for coupled electroelastic fields under the tip. Tip-induced domain switching is mapped on the Landau theory of phase transitions, with domain size as an order parameter. For a point charge interacting with a ferroelectric surface, switching by both first and the second order processes is possible, depending on the charge-surface separation. For a realistic tip, the domain nucleation process is first order in charge magnitude and polarization switching occurs only above a certain critical tip bias. In pure ferroelectric or ferroelastic switching, the late stages of the switching process can be described using a point charge model and arbitrarily large domains can be created. However, description of domain nucleation and the early stages of growth process when the domain size is comparable with the tip curvature radius (weak indentation) or the contact radius (strong indentation) requires the exact field structure. For higher order ferroic switching (e.g., ferroelectroelastic), the domain size is limited by the tip-sample contact area, thus allowing precise control of domain size. (C) 2005 American Institute of Physics.
      327Scopus© Citations 61
  • Publication
    Nanoscale polarization manipulation and imaging of ferroelectric Langmuir-Blodgett polymer films
    (American Institute of Physics, 2007-03-22) ; ; ;
    Piezoresponse force microscopy has been used to manipulate and image polarization of ferroelectric polymer Langmuir-Blodgett films at the nanoscale, achieving polarization control with a resolution below 50 nm and imaging resolution below 5 nm. Individual regions showed square polarization-voltage hysteresis loops, demonstrating bistability of the polarization state. Arbitrary polarization patterns could be repeatedly written and erased with a resolution of 25 to 50 nm, limited by grain size, demonstrating the potential for high-density data storage and retrieval at densities exceeding 250 Gbits/in(2). (c) 2007 American Institute of Physics.
      344Scopus© Citations 86
  • Publication
    Probing the role of single defects on the thermodynamics of electric-field induced phase transitions
    (American Physical Society, 2008-04) ; ; ;
    The kinetics and thermodynamics of first order transitions are universally controlled by defects that act as nucleation sites and pinning centers. Here we demonstrate that defect-domain interactions during polarization reversal processes in ferroelectric materials result in a pronounced fine structure in electromechanical hysteresis loops. Spatially resolved imaging of a single defect center in multiferroic BiFeO3 thin film is achieved, and the defect size and built-in field are determined self-consistently from the single-point spectroscopic measurements and spatially resolved images. This methodology is universal and can be applied to other reversible bias-induced transitions including electrochemical reactions.
    Scopus© Citations 86  387