V. M. Mukhortov

Phase transitions and domain structure in heteroepitaxial ferroelectric (Ba1−xSrx)TiO3//(100)MgO and PbTiO3//(100)MgO thin films

Abstract Heteroepitaxial PbTiO3 and (Ba1−xSrx)TiO3 thin films were obtained by the r.f. sputtering method. The (100) surface cuts of MgO single crystals served as substrates. The films obtained exhibited ferroelectric properties closely similar to those of the ceramic targets. Depending on substrate temperature (Ts) with other deposition parameters constant, heteroepitaxial films of various degrees of perfection of the crystal structure were obtained. Films deposited at a temperature slightly higher than critical temperature (Tcr) for the heteroepitaxy process exhibited an insular growth mechanism while for Ts ⩾ Tcr layer-by-layer growth was found. At room temperature the crystal structure of the PbTiO3//(100)MgO films and of the (Ba1−xSrx)TiO3//(100)MgO films for × ⩽ 0,3 exhibit symmetry of the tetragonal system P4mm. Phase transitions in the (Ba1−xSrx)TiO3//(100)MgO films unlike those in the PbTiO3//(100)MgO films exhibited marked diffusion. The domain structure of the heteroepitaxial films, in comparis...

Memory effects in the structure silicon single crystal-ferroelecltric film

Abstract The memory effects in the structure: (Ba Sr) TiO3 film-silicon single crystal have been studied, It is shown that for explaining them it is necessary to take into account both the natural unipolarity of (Ba, Sr) TiO3 film and the injection of carriers from Si. In terms of the results obtained a conclusion has been made on the possibility of using such structures as currentless cells memory for long-term storage of information.

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.

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.

Phase transitions in polycrystalline and heteroepitaxial ferroelectric films

Experimental evidence concerning the nature of diffuse phase transitions in poly-crystalline and heteroepitaxial films of BaTiO3 and (Ba, Sr)TiO3 with different microscopic strains is presented together with a model for e(T).

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.

Characteristics of growth of complex ferroelectric oxide films by plasma-ion sputtering

An experimental investigation was made of the process of growth of a complex oxide film, such as BaTiO3 or (Ba, Sr)TiO3, by plasma-ion sputtering. It was found that ion bombardment of a ceramic target knocked out neutral excited atoms. These atoms lost energy away from the target by collisions and at a certain critical distance hcr they were capable of oxidation to produce BaO, TiO, TiO2, and SrO. Therefore, depending on the distance between the cathode and the substrate, the “construction” material arrived in the form of atoms or molecules of simple oxides. These two (atomic and molecular) deposition mechanisms corresponded to two mechanisms of synthesis and crystallization differing in respect of the dependences of the growth rate, unit cell parameters, and other structural properties on the deposition temperature. The role of re-evaporation and of oxidation-reduction processes was analyzed.

Polarization switching in metal-dielectric-metal structures with polycrystalline and heteroepitaxial (Ba, Sr) TiO3 films produced by cathode sputtering

The characteristics of polarization switching are studied in metal-dielectric-metal structures as the basis of (Ba, Sr)TiO3 films having a different degree of crystal lattice perfection. The relationships discovered support the conclusions of a phenomenological model of the spreading of the ferroelectric phase transition, according to which microvolumes of the film material are distributed by the magnitude of deformation (the sum of spontaneous deformation and induced defects) and, consequently, by the magnitude of the spontaneous polarization, Curie temperature, coercive field, etc., while the half-width of this distribution is a measure of the average microdefect. The experimentally obtained results show that the items studied have promising applications in active and permanent computer memory devices.