Now showing 1 - 3 of 3
  • Publication
    Real space mapping of polarization dynamics and hysteresis loop formation in relaxor-ferroelectric PbMg1/3Nb2/3O3-PbTiO3 solid solutions
    Polarization switching in ergodic relaxor and ferroelectric phases in the PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) system is studied using piezoresponse force microscopy, single point electromechanical relaxation measurements, and voltage spectroscopy mapping. The dependence of relaxation behavior on voltage pulse amplitude and time is found to follow a universal logarithmic behavior with a nearly constant slope. This behavior is indicative of the progressive population of slow relaxation states, as opposed to a linear relaxation in the presence of a broad relaxation time distribution. The role of relaxation behavior, ferroelectric nonlinearity, and the spatial inhomogeneity of the tip field on hysteresis loop behavior is analyzed in detail. The hysteresis loops for ergodic PMN-10\%PT are shown to be kinetically limited, while in PMN with larger PT content, true ferroelectric hysteresis loops with low nucleation biases are observed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3474961]
      554Scopus© Citations 43
  • Publication
    Piezoresponse force spectroscopy of ferroelectric-semiconductor materials
    Piezoresponse force spectroscopy (PFS) has emerged as a powerful technique for probing highly localized polarization switching in ferroelectric materials. The application of a dc bias to a scanning probe microscope tip in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the tip, detected though the change of local electromechanical response. Here, we analyze the signal formation mechanism in PFS by deriving the main parameters of domain nucleation in a semi-infinite ferroelectric semiconductor material. The effect of surface screening and finite Debye length on the switching behavior is established. We predict that critical domain sizes and activation barrier in piezoresponse force microscopy (PFM) is controlled by the screening mechanisms. The relationships between domain parameters and PFM signal is established using a linear Green's function theory. This analysis allows PFS to be extended to address phenomena such as domain nucleation in the vicinity of defects and local switching centers in ferroelectrics. (c) 2007 American Institute of Physics.
      629Scopus© Citations 67
  • Publication
    Local polarization switching in the presence of surface-charged defects: microscopic mechanisms and piezoresponse force spectroscopy observations
    Thermodynamic description of probe-induced polarization switching in ferroelectrics in the presence of well-localized surface field defects and their effect on local piezoresponse force spectroscopy measurements is analyzed. Corresponding analytical expressions for the free energy, activation energy, nucleation bias, and nucleus sizes are derived. Both numerical calculations and analytical expressions demonstrate that well-localized field defects significantly affect domain nucleation conditions. The signature of the defects in reproducible piezoresponse hysteresis loop fine structure are identified and compared to experimental observations. Deconvolution of piezoresponse force spectroscopy measurements to extract relevant defect parameters is demonstrated. Proposed approach can be extended to switching in other ferroics, establishing a pathway for the understanding of the thermodynamics and kinetics of phase transitions at a single-defect level.
    Scopus© Citations 31  462