E. V. Sviridov

Soft Mode in Heteroepitaxial (Ba, Sr)TiO3MgO Thin Films

Polarized Raman spectra of tetragonally distorted (Ba 1-x Sr,)TiO 3 /MgO ferroelectric films were obtained in special scattering geometries using a micro-Raman set-up. The underdamped E(TO) soft mode was unambiguously observed in the films with x = 0.30 and 0.45. The low-temperature behaviour of the E(TO) soft mode for x = 0.45 was found substantially different from those observed in pure crystals and bulk solid solutions.

The structure and the piezoelectric properties of thin Pb(Zr0.53Ti0.45W0.01Cd0.01)O3 films

Abstract Thin ferroelectric films with thicknesses of (0.6–4.1) × 10−6m have been grown by single-target r.f. sputtering. Powdered lead zirconate-titanate (PZT) type ceramics were used as a target. Microstructure and both dielectric and piezoelectric properties of a thin film depend on its thickness. When the thickness increases, the thermoelastic stresses increase and the influence of the oxide transition layer in the metallic substrate-thin ferroelectric film interface decreases. Thin PZT-type ferroelectric films are characterized by high values of the piezoelectric modulus d33 and weak temperature dependences. All these create an opportunity for their application to electromechanical transducers (e.g. in electroacoustics).

Ferroelectric Film Self-Polarization

In the present paper three mechanisms of self-polarization of ferroelectric crystals are discussed: polarization by the crystal bending, that by the “organized” Phase transition and that by the internal field. It is shown that these mechanisms operate also in the case of films. However, the using of cathode sputtering leads to the appearance of two new mechanisms: polarization by the field biasing the substrate with respect to the gas discharge at the film deposition temperature Ts below the Curie point temperature Tc (Ts Tc).

Thin ferroelectric films of the lead zirconate-titanate type obtained by r.f. sputtering

Abstract Using the method of r.f. sputtering, polycrystalline ferroelectric Pb(Zr0.53Ti0.45W0.01Cd0.01)O3 thin films were obtained with a thickness df = (0.13–11.2) × 10−6m. Study of the crystal structure and microstructure as a function of thickness showed that these thin films have a two-phase structure (phase I of perovskite-type structure and phase II of pyrochlore structure). The concentration of phase II and dimensions of phase I grains and also the degree of perfection of their structure govern the electrical properties of these thin films. The ferroelectric thin films obtained were analysed with respect to their suitability for the construction of memory elements. It was ascertained that this application is feasible but only after subjecting the thin films to annealing in an oxygen atmosphere.

Domain structure of heteroepitaxial ferroelectric films

Domain structure of heteroepitaxial films of (Ba, Sr)TiO3 and PbTiO3 was studied. A correlation between etch-pattern contrast and magnitude of microscopic strains has been established.

The transition layer in polycrystalline PZT films

Abstract The transition nonferroelectric layer with pyrochlore-type structure forming at the initial film growth step was found to exist in as-grown polycrystalline PZT thin films.

Phase transition and domain structure of heteroepitaxial PbTiO3/(001) MgO films

Abstract Heteroepitaxial PbTiO3 films were studied by X-ray diffraction and electron microscopy methods. A model allowing to predict the type of domain structure that forms as a result of the film-substrate mechanical interaction and to determine the c − and a-domain concentrations is suggested.

The structure and dielectric properties of thin PZT-type ferroelectric films with a diffuse phase transition

Abstract By means of r.f. sputtering of the ceramic targets or pressed powder targets with the chemical constitution of Pb (Zr0.52Ti0.46W0.01Cd0.01) O3 the polycrystalline thin ferroelectric films with the perovskite type structure and of thickness df = (1–2, 5) × 10−6 m on metal (stainless steel, platinum) or ceramic (polycor) substrates have been obtained. In case of thin film deposition on steel substrate and on platinum at low temperatures (Tx < 723 K) the nonferroelectric intermediate layer with the same chemical constitution but with the pyrochlore type structure have been created. Results of the X-ray analysis and dielectric investigations (low frequency dispersion) have proved existence of such a structure. The structural phase transition (P4mm ⇄ Pm3m) takes place in the thin ferroelectric films. This is a diffuse type transition and the degree of diffuseness depends on the structural perfection of the thin films. The measure of the structural perfection of the thin films was taken to be the mean ...

Peculiarities of the switching process in polycrystalline thin ferroelectric films of PZT type

One of the basic properties of thin ferroelectric films is the ability to switch polarization under the influence of an external electric field. The application of such thin films as memory devices is based on this phenomenon. The switching process of the thin films has some distinctive features. These include, for example, the dependence of the switching time on the electrode surface and an anomalous variation of the switching time curve with the amplitude of bipolar rectangular electric voltage impulses. To describe the physical nature of these peculiarities a simple model is developed. The qualitative compatibility between experiment and the model is shown on the basis of the Pb(Zr,Ti,B′,B″) O3 (PZT)-type thin films with the chemical constitution Pb(Zr0.53 Ti0.45 W0.01 Cd0.01) O3.

Polarization switching processes in heteroepitaxial (Ba,Sr) TiO3/(001)MgO films

Polarization switching of heteroepitaxial ferroelectric films of 10- to 1200-nm thick with planar electrodes has been studied from the loops of ferroelectric hysteresis. The detected effect of an increase in switched polarization with decreasing film thickness is discussed.