Electrochemical Strain Microscopy with Blocking Electrodes: The Role of Electromigration and Diffusion

Electrochemical strains are a ubiquitous feature of solid state ionic devices ranging from ion batteries and fuel cells to electroresistive and memristive memories. Recently, we proposed a scanning probe microscopy (SPM) based approach, referred as electrochemical strain microscopy (ESM), for probing local ionic flows and electrochemical reactions in solids based on bias-strain coupling. In ESM, the sharp SPM tip concentrates the electric field in a small (10-50 nm) region of material, inducing interfacial electrochemical processes and ionic flows. The resultant electrochemical strains are determined from dynamic surface displacement and provide information on local electrochemical functionality. Here, we analyze image formation mechanism in ESM for a special case of mixed electronic-ionic conductor with blocking tip electrode, and determine frequency dependence of response, role of diffusion and electromigration effects, and resolution and detection limits.Comment: 41 pages, 10 figures, 3 appendices, accepted to J. Appl. Phy

Surface and size effect on fluctuations correlation in nanoparticles with long-range order

Surface and size effect on the order parameter fluctuations and critical phenomena in the intensively studied 3D-confined nanosized systems with long-range order was not considered theoretically, while the calculations for bulk samples and thick films were performed long ago. Since widely used magnetic resonance, diffraction and scattering methods collect information about both macro- and nanosystems via the structural factors, which are directly related with fluctuations correlator, analytical expressions for the correlation function of the order parameter fluctuations seem extremely necessary for quantitative analyses of the experimental data broad spectrum. In the letter we solve the vital problem within Landau-Ginzburg-Devonshire phenomenological approach for the particles of arbitrary shape and consider concrete examples of the spherical and cylindrical ferroic nanoparticles. Allowing for the strong surface energy contribution, analytical expressions derived for Ornstein-Zernike correlator of the long-range order parameter fluctuations in 3D-confined system, dynamic generalized susceptibility, relaxation times and correlation radii discrete spectrum are principally different from those known for bulk system. Besides the great importance of the fluctuations correlation function for the analyses of scattering and magnetic resonance experimental spectra, proposed expression for fluctuations strength defines the fundamental limit of phenomenological theory applicability for 3D-confined nanosystems.Comment: 15 pages, 2 figures, 1 appendi

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