Publications by Alexander Tagantsev

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The phenomenon of time-dependent polarization loss in poled ferroelectric capacitors, also known as retention, represents one of the most important reliability issues for ferroelectric nonvolatile memories. In a number of publications different ways to con ...

The thermal stability of amorphous ionic solids is usually attributed to kinetic considerations related to mass transport. However, there are a number of amorphous ionic solids, which have recently been described, whose unusual resistance to nucleation and ...

We report a type of structural phase transitions in dielectric materials: the triggered incommensurate (IC) transition. We demonstrate evidence for such a transition in the perovskite antiferroelectric PbHfO3 by means of single-crystal x-ray diffraction, d ...

The effects of niobium doping on the hysteresis parameters of sol-gel Pb-1.1-x/2(Zr0.53Ti0.47)(1-x)NbxO3 (0 < x < 0.05) have been reported fbr two sets of films with analogous grain size and degree of (111) texture but with different surface microstructures. For both sets, a strong continuous decay of the remnant and maximum polarizations and slope of the hysteresis loop at the coercive field was observed with increasing niobium concentration. The held dependence of the remnant polarization for any given ni

The influence of flexoelectric coupling on the internal structure of neutral domain walls in the tetragonal phase of perovskite ferroelectrics is studied. The effect is shown to lower the symmetry of 180 degrees walls which are oblique with respect to the ...

The phenomenon of polarization imprint consisting of the development of a preferential polarization state in ferroelectric films is known as one of the major issues impacting the development of high density ferroelectric memories. According to the commonly accepted scenario, the imprint is related to the charge injection and charge accumulation in the nearby-electrode passive layer of the ferroelectric film. Recent studies demonstrated that the coercive voltage shift induced by the imprint exhibits a nonlin

Head-to-head and tail-to-tail 180 degrees domain walls in a finite isolated ferroelectric sample are theoretically studied using Landau theory. The full set of equations, suitable for numerical calculations, is developed. The explicit expressions for the polarization profile across the walls are derived for several limiting cases and wall widths are estimated. It is shown analytically that different regimes of screening and different dependences for the width of charged domain walls on the temperature and p

Structural and dielectric properties of epitaxial SrTiO3 (STO) thin films on LaAlO3 substrates fabricated by a two-step growth technique using pulsed laser deposition were investigated by in situ and ex situ observations in terms of strain relaxation from ...

The domain nucleation and growth during polarization switching in Pb(Zr,Ti)O-3 (PZT) ferroelectric thin film capacitors with Pt top (TE) and bottom electrodes (BE) were studied by means of atomic force microscopy (AFM). The experimental configuration used in this study differs from that conventionally used (AFM tip/PZT/BE) where the AFM tip acts as a positionable TE. A small ac voltage was applied between the electrodes with a step by step increasing dc bias voltage. The induced piezoelectric vibration was

Mechanisms of polarization switching and fatigue in (Pb, La)(Zr, Ti)O-3 (PLZT) films are studied by comparative analysis of degradation and leakage conduction of PLZT capacitors with Pt, SrRuO3 (SRO), and layered Pt/SRO (80/5 nm) electrodes. It is found that the asymmetrical Pt/SRO/PLZT/Pt structure exhibits a good fatigue performance in combination with low leakage like that on identically processed Pt/PLZT/Pt capacitor. This asymmetrical structure exhibits very unusual dependence of the endurance of switc

The internal structure of neutral 180 degrees domain walls in perovskite-type ferroelectrics is studied in terms of Landau theory taking into account electromechanical coupling. The study is focused on the wall bistability, a factor of potential interest f ...

The properties of interstitial and substitutional Li in wurtzite ZnO are modeled using hybrid density functional calculations. We investigate the impact of the band-gap error on the formation energies of the two defects and their dependence on the Fermi le ...

Using pulsed-laser deposition, a two-step growth technique was applied to epitaxial SrTiO3 (STO) thin films on LaAlO3 substrates providing a way to obtain an effective strain relaxation in these films otherwise strained due to lattice mismatch between film ...

Strong coupling among external voltage, electrochemical potentials, concentrations of electronic and ionic species, and strains is a ubiquitous feature of solid statemixed ionic-electronic conductors (MIECs), the materials of choice in devices ranging from electroresistive and memristive elements to ion batteries and fuel cells. Here, we analyze in detail the electromechanical coupling mechanisms and derive generalized bias-concentration-strain equations for MIECs including contributions of concentration-dr

The expressions for the spontaneous polar contribution delta n (i) (s) to the principal values of the refractive index due to the quadratic electro-optic effect in ferroelectrics have been considered within the phenomenological approach taking into account ...

Strontium barium niobate thin films have been deposited by pulsed laser deposition on (111)-textured Pt films, p-doped Si(I 00) and Nb doped STO (SrTiO3) single crystals. The deposition parameters were optimized for obtaining phase pure (001)-oriented films from stochiometric targets. The samples were annealed in oxygen to improve top electrode adhesion and reduce oxygen vacancies. The SBN/substrate interfaces were investigated by means of TEM combined with EDAX chemical analysis. Growth on silicon resulted

Leakage conduction of Pt-Pb(ZrXTi:(1-X))O-3-Pt capacitors is studied by means of different measuring techniques and analyzed in terms of semiconductor properties of the system. Based on the experimental data, it is concluded that two different regimes of carrier injection (with the critical electric field of the crossover between these regimes being independent of the measuring technique) are responsible for true leakage conduction in Pt-Pb(ZrXTi1-X)O-3-Pt films. For interpretation of the experimental resul

We study the electrodynamics of a superlattice that consists of two kinds of layers: the layers of a type-II superconductor and the layers of a normal metal in a perpendicular magnetic field. The problem is treated in the framework of London electrodynamics taking into account simultaneously the nonlocality of the intervortex interaction and the Abrikosov vortex elasticity. The dependence of the surface impedance Z on the dc-magnetic-field induction B much less than H(c2) (H(c2) is the upper critical field)

We review the current theory of intrinsic dielectric loss, that is the loss in a perfect crystal due to anharmonic interaction of a.c. electric field with the phonon system of the crystal. Both ordinary dielectrics and displacive ferroelectrics are considered. The theory predicts dependence of the loss on frequency omega and temperature T. This dependence is very sensitive to the symmetry of the crystal. For ordinary dielectrics, the results are presented and tabulated for all 32 symmetry groups, except for

The dependence of the permittivity, on uniaxial pressure of ceramics in the paraelectric, ferroelectric and relaxer phases has been investigated for BaTiO3, Pb(ZrTi)O-3 and Pb(Mg1/3Nb2/3)O-3. In the paraelectric ic phase, upon the application of stress, a reversible decrease in the permittivity is observed. In the ferroelectric phase, the observed behaviors can be divided in two classes depending on the type of ionic defects present in the ceramics. Both behaviors are characterized by an instantaneous incre

Alexander Tagantsev

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Physical model of retention and temperature-dependent polarization reversal in ferroelectric films

Formation and thermal stability of quasi-amorphous thin films

Triggered incommensurate transition in PbHfO3

Use of ferroelectric hysteresis parameters for evaluation of niobium effects in lead zirconate titanate thin films

Bichiral structure of ferroelectric domain walls driven by flexoelectricity

Nature of nonlinear imprint in ferroelectric films and long-term prediction of polarization loss in ferroelectric memories

Head-to-head and tail-to-tail 180^{°} domain walls in an isolated ferroelectric

Structural and dielectric properties of strain-controlled epitaxial SrTiO3 thin films by two-step growth technique

High resolution study of domain nucleation and growth during polarization switching in Pb(Zr,Ti)O-3 ferroelectric thin film capacitors

Top-interface-controlled switching and fatigue endurance of (Pb, La)(Zr,Ti)O-3 ferroelectric capacitors

Bistability of ferroelectric domain walls: Morphotropic boundary and strain effects

A hybrid density functional study of lithium in ZnO: Stability, ionization levels, and diffusion

Strain relaxation of epitaxial SrTiO3 thin films on LaAlO3 by two-step growth technique

Thermodynamics of electromechanically coupled mixed ionic-electronic conductors: Deformation potential, Vegard strains, and flexoelectric effect

Contribution of spontaneous polarization and its fluctuations to refraction of light in ferroelectrics

Microstructural and electrical properties of (Sr,Ba)Nb2O6 thin films grown by pulsed laser deposition

Physical origin of conduction in PZT thin films

Dc-Magnetic-Field Dependence of the Surface Impedance of a Multilayer Superconductor System in the Mixed-State

Intrinsic Dielectric Loss in Crystals

Uniaxial stress dependence of the permittivity of electroceramics