3,145 research outputs found
Pyroelectric response of ferroelectric nanoparticles: size effect and electric energy harvesting
The size effect on pyroelectric response of ferroelectric nanowires and
nanotubes is analyzed. The pyroelectric coefficient strongly increases with the
wire radius decrease and diverges at critical radius Rcr corresponding to the
size-driven transition into paraelectric phase. Size-driven enhancement of
pyroelectric coupling leads to the giant pyroelectric current and voltage
generation by the polarized ferroelectric nanoparticles in response to the
temperature fluctuation. The maximum efficiency of the pyroelectric energy
harvesting and bolometric detection is derived, and is shown to approach the
Carnot limit for low temperatures.Comment: 17 pages, 4 figures, 1 Appendi
Electromechanical Probing of Ionic Currents in Energy Storage Materials
The electrochemical processes in energy storage materials are generally
linked with changes of molar volume of the host compound. Here, the frequency
dependent strain response of 1D electrochemically active systems to periodic
electric bias is analyzed. The sensitivity and resolution of these
electrochemical strain measurements are compared to the current-based
electrochemical impedance spectroscopy. The resolution and detection limits of
interferometric and atomic force microscopy based systems for probing
electrochemical reactions on the nanoscale are analyzed.Comment: 12 pages, 4 figures, 2 tables, 2 appendices, submitted to Appl. Phys.
Let
Effect of the Intrinsic Width on the Piezoelectric Force Microscopy of a Single Ferroelectric Domain Wall
Intrinsic domain wall width is a fundamental parameter that reflects bulk
ferroelectric properties and governs the performance of ferroelectric memory
devices. We present closed-form analytical expressions for vertical and lateral
piezoelectric force microscopy (PFM) profiles for the conical and disc models
of the tip, beyond point charge and sphere approximations. The analysis takes
into account the finite intrinsic width of the domain wall, and dielectric
anisotropy of the material. These analytical expressions provide insight into
the mechanisms of PFM image formation and can be used for quantitative analysis
of the PFM domain wall profiles. PFM profile of a realistic domain wall is
shown to be the convolution of its intrinsic profile and resolution function of
PFM.Comment: 25 pages, 5 figures, 3 tables, 3 Appendices, To be submitted to J.
Appl. Phy
Mesoscopic mechanism of the domain wall interaction with elastic defects in ferroelectrics
The role of elastic defects on the kinetics of 180-degree uncharged
ferroelectric domain wall motion is explored using continuum time-dependent LGD
equation with elastic dipole coupling. In one dimensional case, ripples, steps
and oscillations of the domain wall velocity appear due to the wall-defect
interactions. While the defects do not affect the limiting-wall velocity vs.
field dependence, they result in the minimal threshold field required to
activate the wall motions. The analytical expressions for the threshold field
are derived and the latter is shown to be much smaller than the thermodynamic
coercive field. The threshold field is linearly proportional to the
concentration of defects and non-monotonically depends on the average distance
between them. The obtained results provide the insight into the mesoscopic
mechanism of the domain wall pinning by elastic defects in ferroelectrics.Comment: 18 pages, 6 figures, 1 appendi
Probing the role of single defects on the thermodynamics of electric-field induced phase transitions
The kinetics and thermodynamics of first order transitions is 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.Comment: 34 pages,4 figures, high quality figures are available upon request,
submitted to Phys. Rev. Let
Tuning the Polar States of Ferroelectric Films via Surface Charges and Flexoelectricity
Using the self-consistent Landau-Ginzburg-Devonshire approach we simulate and
analyze the spontaneous formation of the domain structure in thin ferroelectric
films covered with the surface screening charge of the specific nature
(Bardeen-type surface states). Hence we consider the competition between the
screening and the domain formation as alternative ways to reduce the
electrostatic energy and reveal unusual peculiarities of distributions of
polarization, electric and elastic fields conditioned by the surface screening
length and the flexocoupling strength. We have established that the critical
thickness of the film and its transition temperature to a paraelectric phase
strongly depend on the Bardeen screening length, while the flexocoupling
affects the polarization rotation and closure domain structure and induces
ribbon-like nano-scale domains in the film depth far from the top open surface.
Hence the joint action of the surface screening (originating from e.g. the
adsorption of ambient ions or surface states) and flexocoupling may remarkably
modify polar and electromechanical properties of thin ferroelectric films.Comment: 33 pages, 5 figure
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