An experimental study of the crystal structure and ferroelectric properties of <110>-textured lead zirconate titanate films with a fine variation in their composition (with a change in the elemental ratio of zirconium and titanium atoms within 1.5%) near the morphotropic phase boundary revealed jump-like changes in the pseudocubic lattice parameter, dielectric permittivity and residual polarization. It is assumed that the observed anomalies correspond to a morphotropic transition from a rhombohedral to a mixture of tetragonal and monoclinic phases.

The features of the microstructure of radiant spherulites in lead zirconate titanate thin films are studied using scanning electron and nonlinear optical microscopy by varying the blocks size of the perovskite structure. It is shown that with an increase in the radius of the spherulite (or the size of blocks), the angle of rotation of the growth axis increases, the speed of the angle of rotation, and the magnitude of the signal of the second optical harmonic It is assumed that the reasons determining specifics of the structure and signal of the second optical harmonic are associated with a change in the magnitude of mechanical stresses in the films that arise due to a change in the phase density at perovskite phase crystallization from low-temperature pyrochlore phase or at perovskite phase recrystallization

The microstructure and pyroelectric properties of AlxGa1-xN composite epitaxial layers grown on SiC/Si(111) and SiC/Si(110) hybrid substrates by the chloride-hydride epitaxy have been studied. The phenomenon of spontaneous formation of a system of heterojunctions consisting of periodic AlxGa1-xN layers of different composition located perpendicular to the direction of growth, was discovered during the growth of layers. Measurements of the pyroelectric coefficients of these heterostructures have shown that regardless of the orientation of the initial Si substrate and their pyroelectric coefficients have close values of the order of γ ~ (0.7-1)•10-10 С/cm2K. It is shown that to increase the magnitude of the pyroresponse it is necessary to deposit an AlN layer with a thickness exceeding 1 μm on the AlxGa1-xN/SiC/Si surface. This leads to record values of the pyroelectric coefficient γ ~ 18•10-10 С/cm2K for AlN crystals and films

In self-polarized lead zirconate titanate thin films formed on platinized silicon substrates, a significant increase in the internal electric field was observed as a result of long-term aging. To explain this phenomenon, a mechanism is proposed for the formation of the internal field associated with the diffusion of charged oxygen vacancies, which, in turn, is due to the action of a mechanical stress gradient. The diffusion coefficient of charged oxygen vacancies was estimated to be ∼ 3 × 10–16 cm2/s.

The microstructure, dielectric, and pyroelectric properties of AlxGa1-xN composite epitaxial layers grown on SiC / (111) Si substrates by chloride-hydride epitaxy are studied. In the process of layer growth, the phenomenon of spontaneous formation of heterojunctions was discovered. Based on AlxGa1-xN epitaxial layers, a material has been obtained which currently has one of the highest pyroelectric coefficients for crystals (or thin films) of aluminum nitride.

Using nonlinear optical microscopy, single-phase (perovskite) and double-phase (perovskite+pyrochlore) thin films of lead zirconate titanate deposited on Pt/TiO2/SiO2/Si substrates by the method of high-frequency magnetron sputtering at different distances of the substrate targets (D=30-70 mm) were studied. An inhomogeneous distribution of the second harmonic signal in spherulite perovskite islands was detected, including an increase in the signal at the perovskite/pyrochlore boundary, which may be due to an inhomogeneous distribution of mechanical stresses. The reasons for strong changes in the signal of the second harmonic, its relationship to changes in the character of the spherulite structure and conditions of film deposition when the distance of the target-substrate varies are discussed.

Two-layer thin lead zirconate titanate films in which the lead content differed by 20% were formed by radio-frequency magnetron deposition under variation of the working gas pressure. A comparative study of the phase state, composition, and dielectric properties of bilayer structures differing in the sequence of layers deposition has been carried out. It is shown that, depending on the order of the layers, the conditions of crystallization of the perovskite phase and the unipolar properties of the films change significantly.

AbstractVariation of the working gas pressure (from 8 to 2 Pa) during RF magnetron sputtering deposition of thin perovskite lead zirconate titanate (PZT) films revealed strong changes in their lead content, which decreased below the stoichiometric level and led to the formation of a two-phase (perovskite–pyrochlore) structure upon subsequent high-temperature annealing. Measurements of the composition of perovskite islands in the two-phase films showed that the lead content in these islands was equal to or greater than stoichiometric. These results lead to the conclusion that the obtained PZT films are free of lead vacancies.

The dielectric and polar properties of thin films of aluminum nitride (AlN) epitaxially grown on variously oriented p-type silicon substrates with a buffer sublayer of silicon carbide (SiC), as well as on vicinal planes, are studied. According to the results of studies of the polar properties by two independent methods — the dynamic pyroelectric effect and piezoelectric force microscopy, it was shown that the use of a SiC buffer layer significantly improves the polar properties of thin layers of aluminum nitride.

The features of the microstructure and piezoelectric response of perovskite islands in the matrix of the pyrochloric phase in thin lead zirconate titanate films formed by the method of radio-frequency magnetron sputtering are investigated. The radial heterogeneity of the surface morphology of the islands and the piezoelectric response is revealed. The role of two-dimensional mechanical stresses acting on a thin film from the side of the silicon substrate is discussed.

AbstractThe element composition modification is experimentally studied in PZT thin films obtained via the RF magnetron sputtering with variable working gas pressure. The experimental data were interpreted through the statistic simulation of thermalization and diffusion of sprayed Pb, Zr, and Ti atoms during the ion-plasma deposition of PZT thin films. The simulation data are shown to adequately describe (within the limits of 5%) the change in element composition at various pressures of the gas environment. The study conducted enables one to produce PZT thin films with a set element composition, which is essential for optimizing the electric and physical properties of solid solutions at the morphotropic phase boundary.

Рассматриваются причины изменения ориентации вектора естественной униполярности в результате нагревания до температуры Кюри тонкопленочного конденсатора Pt/PZT/Pt (PZT --- цирконат-титанат свинца), сформированного на подложке TiO2/SiO2/Si. Тонкие слои PZT, содержащие незначительный избыток оксида свинца, сформированы ex situ методом высокочастотного магнетронного распыления при вариации температуры отжига (кристаллизации фазы перовскита) в диапазоне 580-650oC. Предполагается, что реориентация вектора униполярности в слое PZT вызвана сменой механизма кристаллизации фазы перовскита с ростом температуры отжига. Работа выполнена при частичной финансовой поддержке Министерства образования и науки РФ (грант 14.Z50.31.0034) и гранта РФФИ N 16-02-00632.