This study discusses the conditions for the occurrence of two-dimensional superconductivity under the action of an electric field on an La 2 – x Sr x CuO 4 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.

Показано, что при воздействии электрического поля на пластинку высокотемпературного сверхпроводника при определенных условиях может возникнуть квазидвумерная сверхпроводимость. Это происходит, если в отсутствие электрического поля при температуре меньше максимальной температуры сверхпроводящего перехода концентрация носителей в пластине находится вне области существования сверхпроводимости. Изучение проведено для пластины лантан-стронциевого купрата при различных концентрациях дырок, температурах и разностях потенциалов. Оказалось, что квазидвумерный сверхпроводящий слой возникает вблизи поверхности пластины. Толщина сверхпроводящего слоя составляет несколько ангстрем и в исследованном диапазоне не зависит от величины поля. Его толщина зависит лишь от концентрации дырок и температуры. В то же время расстояние сверхпроводящего слоя от края пластины является функцией всех трех факторов. Сформулированы условия проведения эксперимента.

Binary mixtures of oxides structured at the nanoscale are considered using the example of CeO 2 –In 2 O 3 . The role of catalytically active CeO 2 nanoclusters is clarified during charge distribution in nanoparticles (In 2 O 3 ) with a high concentration of electrons. The flow of oxygen atoms from the CeO 2 nanoclusters on nanoparticles In 2 O 3 , which enhances the inhomogeneous distribution of the conduction electrons in the In 2 O 3 nanoparticle and depletes the near-surface layer, is taken into account. It is shown that since the conductivity of the system is determined by the near-surface electron density, the film resistance increases with an increase in the concentration of the CeO 2 .

The electronic structure of nanoparticles in binary mixtures of oxides are considered by the example of CeO2-In2O3. The effect of catalytically active CeO2 nanoclusters on charge distribution in nanoparticles with a high concentration of conduction electrons (In2O3) is studied. The spillover of oxygen atoms from CeO2 nanoclusters to In2O3 nanoparticles, which enhances the inhomogeneous distribution of conduction electrons in the In2O3 nanoparticle, is taken into account, and it is shown that exactly spillover leads to depletion of the near-surface layer. The film resistance rises with an increase in the CeO2 concentration, due to a decrease in the near-surface electron density in In2O3 nanoparticles and the overlap of the current flow paths by CeO2 nanoclusters. An expression for the temperature dependence of a nanostructured film resistance is found, taking into account the inhomogeneous distribution of electrons in nanoparticles. The temperature dependence of the CeO2-In2O3 film was measured and the results were compared with theory. A good agreement between theory and experiment was obtained.

Abstract The theory of occurrence of superconductivity in the plate of high-temperature superconductor under electric field vertical to it, when the carrier concentration lies outside of the region of existence of superconductivity at the temperature T < $$T_{{\text{c}}}^{{\max }}$$ , was developed. The calculation was carried out for the layer of lanthanum strontium cuprate under the fields of 10^–1 V/nm ≥ E ≥ 10^–2 V/nm at various temperatures and hole concentrations. It was demonstrated that the quasi-two-dimensional superconducting layer of several Angstrom in thickness occurs near surface of the plate, moreover thickness of this layer does not depend on magnitude of the field, and depends only on temperature and on hole concentration.

The study investigates the possible origin of electric field effect on the rate of chemical reactions. The geometry of the considered problem mirrors the shape of surface roughness elements as well as the tip of a scanning tunneling microscope (STM) used to study the peculiarities of chemical reaction in an external electrostatic field. The results show that the actual field near truncated cone acting on the chemical system significantly exceeds the average external field. It is shown that in the calculation of the effect of electric field on the rate of chemical reactions, the increase in the electric field near nanoscale protrusions of the metal surface, in particular, near the STM needle, should be taken into account. These results are used to study the Diels-Alder reaction under the influence of electric field.

The theory of occurrence of superconductivity in the plate of high-temperature superconductor under electric field vertical to it, when the carrier concentration lies outside of the region of existence of superconductivity at the temperature T < $$T_{{\text{c}}}^{{\max }}$$, was developed. The calculation was carried out for the layer of lanthanum strontium cuprate under the fields of 10–1 V/nm ≥ E ≥ 10–2 V/nm at various temperatures and hole concentrations. It was demonstrated that the quasi-two-dimensional superconducting layer of several Angstrom in thickness occurs near surface of the plate, moreover thickness of this layer does not depend on magnitude of the field, and depends only on temperature and on hole concentration.

The electric field and charge distributions in a nanosized truncated metal cone in a strong electric field have been found. The geometry of the problem corresponds to surface roughness elements and a scanning tunneling microscope tip. The electron density along the cone axis is shown to change dramatically, by tens of percent. The field penetrates deep into the metal tip to distances of the order of a nanometer. The position of the Fermi level near the upper base of the cone changes noticeably. The barrier through which the electrons are tunneled upon entry into or exit from the tip is shown to be asymmetric and to depend on the sign of the external electric field.

The article by Barami, and Ghafarinia (Sensors and Actuators B: Chemical, 293 (2019) 31–40) considers the electric potential and surface oxygen ion density in metal oxide grains. However the problem was solved using the wrong assumptions. Specifically, the density of ionized (positively charged) donors along the nanoparticle radius was assumed to be constant, equal to the density in the massive semiconductor, and the concentration of negatively charged oxygen ions on the surface of the nanoparticle was chosen arbitrarily. The implication of the assumptions are discussed and suggestions are made for the correct approach.

The theory is developed of sensory response to reducing gases of nanostructured semiconductor oxides such as In2O3 with large concentration of electrons in the conduction band. The charge distribution in nanoparticles is determined by the functional relationship between the density of negative and positive charges inside the nanoparticles and electrons on the surface. The capture of conduction electrons by adsorbed oxygen atoms causes redistribution of electrons in the nanoparticles, thereby decreasing the near-surface electron density and the conductivity of the system. Thus, there is a functional relationship between negative charge on the surface and charge structure inside the nanoparticle, which has to be considered. The conditions for the association-dissociation reactions of oxygen molecules on the surface also change. On adsorption of a reducing gas, the O- ions react with the gas molecules and the electrons are released into the volume of the nanoparticles. The conductivity of the system thereby increases, which constitutes the sensory effect. The radial distributions of the conduction electrons and electrostatic potential in a nanoparticle are here calculated as a function of the hydrogen concentration in the ambient air. A kinetic scheme is developed of chemical reactions corresponding to the above sensory mechanism, and the associated equations are solved. As a result, the theoretical functional relationships of sensitivity to temperature and hydrogen concentration are established. The theoretical results are in good agreement with the experimental data.

A theory of sensor response on reducing gases of nanoscale-structured semiconducting oxides with the high concentration of conduction-band electrons has been developed (modeled on In2O3). The distribution of charges in nanoparticles is determined by the functional relationship of the density of negative and positive charges in nanoparticles and electrons on their surface. The capture of conduction electrons by adsorbed oxygen atoms causes electron redistribution in nanoparticles, such that the near-surface density of electrons and the conductivity of the system decrease. In this case, the conditions of the association and dissociation of oxygen molecules on the surface also change. During the adsorption of reducing gases (H2, CO), atomic oxygen ions react with them and electrons are released that enter bulk nanoparticles. The conductivity of the system increases, which corresponds to the sensor effect. A kinetic scheme of chemical reactions, which corresponds to the that described above, has been plotted and corresponding equations were solved. As a result, theoretical dependences of the sensitivity of sensor on the temperature and pressure of hydrogen were found, which agree well with experimental curves at qualitative and quantitative level.

The distributions of electrons and positive charges within a spherical semiconductor nanoparticle with surface electron traps in a uniform applied electric field are studied. The minimization of the total free energy gives the resulting effective electric field, which depends on the densities of donors and surface traps, as well as on the distance from the center of the nanoparticle. It is shown that the near-surface field at a relatively low donor density in the region of its entrance to the nanoparticle significantly differs from that in the region of its departure from the nanoparticle. The induced dipole moment of the nanoparticle is calculated and different contributions to it are determined. The ranges of applicability of the results are indicated.

A rigorous calculation of the thermodynamic equilibrium of the metal–external charge system has shown that the generally accepted assumption that the electric field does not penetrate into the metal is incorrect. In reality, the field penetrates deep into the metal, and the interaction of the charge with the metal is noticeably stronger than the standard interaction with the electric image of the charge. It depends on the characteristics of the electronic system of the metal, on the sign of the charge, and, somewhat differently than the standard one, depends on the magnitude of the charge.