Vol 42, No 7 (2023)

This study discusses the conditions for the occurrence of two-dimensional superconductivity under the action of an electric field on an La2 – xSrxCuO4 plate at a temperature lower than the maximum temperature of the superconducting transition, but when the concentration of charge carriers falls outside the superconductivity range. The study is carried out for a lanthanum-strontium cuprate plate at various hole concentrations, as well as temperature, and potential differences. A quasi-two-dimensional superconducting layer arises near the surface of the plate. The thickness of the superconducting layer is several angstroms and independent of the field strength in the range investigated. The thickness depends only on the concentration of holes and temperature. In addition, the distance of the superconducting layer from the edge of the plate is found to be a function of all three factors. The conditions used for conducting the experiment are also formulated.

The structure of a device designed to detect X-ray and optical photons ascending from a sample irradiated with synchrotron radiation or X-ray tube radiation and the principles of its operation are described. The operation of the device consists of determining the delay time of the specified optical photons relative to the X-ray photons. Block diagrams of the main components of the device, outlining the principles of their operation, are given: a monophoton X-ray sensor, a monophoton optical sensor, and a unit for determining the time delay. The areas of scientific and applied use of information obtained with the help of the considered device are indicated.

Polylactide is a biodegradable polymer that is increasingly used in the production of medical devices and environmentally friendly packaging. The search for new catalysts for the synthesis of polylactide that do not contain toxic tin and provide a polymer with a controlled set of properties is an urgent problem. In this study, a catalytic complex based on titanium (IV) is synthesized and characterized. The kinetics of the polymerization of L-lactide in the presence of this catalyst is studied by differential scanning calorimetry (DSC), the reaction enthalpy (–125.1 ± 1.5 J/g) is determined, and the kinetic parameters of the Arrhenius equation are calculated (Ea = 95.7 ± 7.5 kJ/mol, lnAeff = 22.7 ± 1.9).

Poly(p-xylylene)–molybdenum oxide nanocomposite thin films of different thicknesses and inorganic filler content are synthesized by low-temperature vapor deposition polymerization. The structure of the nanocomposites and its evolution during thermal annealing is studied by wide angle X-ray scattering and X-ray absorption spectroscopy. It is found that the molybdenum oxide nanoparticles are amorphous in both the as-deposited and annealed composite films. The short-range order characteristic of orthorhombic molybdenum trioxide is preserved in the nanoparticles; however, a noticeable disordering of the structure together with a decrease in the effective oxidation state of molybdenum are revealed. Both an increase in the filler content and thermal annealing lead to a decrease in the bandgap of the composites, which is related to the increase in the nanoparticle size. It is shown that thermal annealing improves the stability of the resistive switching (RS) characteristics in memristors based on the synthesized nanocomposites, which creates an opportunity for the application of these materials as the active layer of memristive devices.

Density functional theory (DFT) modeling of the adsorption of atomic oxygen and hydrogen on the surface of palladium nanoparticles on graphite substrates with various defects is used to calculate the binding energies of adatoms and changes in the density of states of metal atoms upon interaction with adatoms. It is established that the adsorption of oxygen and hydrogen does not have more energetically favorable or stable adsorption sites on the surface of the nanoparticle, such as the interface with the substrate or the top, which is consistent with the results of the scanning tunneling microscopy and spectroscopy (STM/STS) experiments.

In this study, the specific features of the kinetics of singlet fission (SF)—i.e., spontaneous splitting of the excited singlet state into a pair of triplet (T) excitons (TT-pair)—in anisotropic molecular crystals are analyzed in detail. These features are known to be primarily determined by the TT-annihilation of the created TT-pairs (migrating in the crystals). In our analysis, the kinetics of annihilation-affected SF processes is described in the two-state model (TSM), in which the interaction of migrating T-excitons is associated with transitions between two kinetic states of TT-pairs: [TT]-state of coupled TT-pairs and [T+T]-state of freely migrating T-excitons. The TSM makes it possible to represent the effects of migration and interaction on SF-kinetics in terms of the lattice Green’s functions, for which the analytical formulas are obtained in this study. The TSM is applied to the analysis of SF-kinetics in the rubrene single crystals recently measured in a wide time range. The analysis provides detailed information on some characteristic kinetic properties of SF processes in anisotropic crystals. It is shown, for example, that the formation of the [TT]-state in the SF process results in some distortion of the shape of the SF kinetic dependence at short times (of the order of the primary-stage time of SF kinetics). Is also demonstrated that the anisotropy of T-exciton migration manifests itself in some characteristic features of SF kinetics at long times.