I. M. Shmytko

Oxygen doping of HTSC and resistive switching in HTSC-based heterostructures

The studies of the bipolar resistive switching effect in thin film heterojunctions (YBa2Cu3O7−δ/Ag) and (Nd 2−xCexCuO4−y/Ag) have exhibited the role of oxygen as a doping element in hole- and electron-doped HTSC compounds.

Nd2 − xCexCuO4 − y/Nd2 − xCexOy boundary and resistive switchings in mesoscopic structures on base of epitaxial Nd1.86Ce0.14CuO4 − у films

Reverse and stable bipolar resistive switching effect was observed in planar NdCeCuO - NdCeO - Ag heterostructures. It was shown that the current voltage charactereriscs of the BRSE observed has a diode character. Simulations were used to consider the influence of the nonuniform distribution of an electric field at the interface of a heterojunction on the effect of bipolar resistive switching in investigated structures. The inhomogeneous distribution of the electric field near the contact edge creates regions of higher electric field strength which, in turn, stimulates motion and redistribution of defects, changes of the resistive properties of the whole structure and formation of a percolation channel.

NdCeCuO - NdCeO boundary and resistive switchings in mesoscopic structures on base of epitaxial NdCeCuO films

Reverse and stable bipolar resistive switching effect was observed in planar NdCeCuO - NdCeO - Ag heterostructures. It was shown that the current voltage charactereriscs of the BRSE observed has a diode character. Simulations were used to consider the influence of the nonuniform distribution of an electric field at the interface of a heterojunction on the effect of bipolar resistive switching in investigated structures. The inhomogeneous distribution of the electric field near the contact edge creates regions of higher electric field strength which, in turn, stimulates motion and redistribution of defects, changes of the resistive properties of the whole structure and formation of a percolation channel.

Influence of nanoparticles of cesium sulfate and deformation on structure, vibration spectra, and luminescence of polystyrene

Significant changes in infrared absorption spectra of polystyrene upon the addition of cesium sulfate nanoparticles to it are observed, which is due to two variants of attachment of organic molecules to nanoparticles (through hydrogen and pi bonds). The relation between the bonds changes significantly during deformation of polystyrene/cesium sulfate composite owing to differences in the mechanical strength thereof. In its turn, the differences in atomic and electronic bond structures result in a significant differentiation of their influence on light emission processes, making it possible to control the scintillation characteristics of polystyrene/nanoparticle composites via regulating their composition and morphology.

Deformation behavior features of composite of polystyrene with cesium sulfate filler during ultraviolet and X-ray irradiation

A noticeable increase in radiation resistance of polystyrene upon the addition of cesium sulfate particles is found. This is due to the fact that the fragments of polystyrene molecules fixed by filler particles do not diverge at radiation breakage of interatomic bonds, keeping a high possibility of recovery thereof. When studying X-ray luminescence of this composite, it is found that its deformation results in the decrease in the proportion of luminescence of organic luminophores, which indicates direct involvement of contact areas between the particles and molecules in the transfer of energy of electronic excitations according to the Dexter or Frerichs mechanism.

Optical phonon spectra of lutetium fluoride, oxyfluoride, and lutetium oxide nanoparticles

Nano-and microcrystalline LuF3 phases have been synthesized with particle sizes of 30 nm and 30 μm, respectively. Analysis of the IR reflection spectra measured at T = 300 K showed that the nanophase differs from the microcrystalline phase by reduced optical phonon frequencies. It is established that annealing of the LuF3 nanophase in air leads to the formation of nanoparticles of the LuO1 − xF1 + 2x and Lu2O3 compositions. The IR reflection spectra of the nanophases indicate that these nanoparticles consist of an oxyfluoride core surrounded with a Lu2O3 shell; the latter is in the strained state.

Resistive switching in mesoscopic heterostructures based on Nd 2– x Ce x CuO 4– y epitaxial films

Reversible and stable bistable resistive switching were observed in planar-type junctions Nd2–xCexCuO4–y/Nd2–xCexO1.75/Ag. It was shown that current transport in such junctions has a diode character with Schottky-like barriers in highly doped semiconductors. It was revealed that the key factor for switching is the presence of the second phase Nd2–xCexO1.75, deficient in oxygen, epitaxially germinated at the Nd2–xCexCuO4–y surface.

Resistive switchings and diode properties of heterostructures based on epitaxial superconducting Nd2–xCexCuO4–y films

Reversible and reliable bistable resistive switchings are observed in planar-type Nd2–xCexCuO4–y/Nd2–xCexO1.75/Ag junctions based on the Nd2–xCexCuO4–y superconducting films. Investigation of electronic structure of surface of the Nd0.5Ce0.5O1.75/Nd2–xCexCuO4–y via high-resolution X-ray photoelectron spectroscopy and atomic force microscopy (AFM) show that the key factor for the switchings is the presence of an oxygen-deficient Nd2-xCexO1.75 phase, epitaxially intergrown on surfaces of Nd2–xCexCuO4–y.

Frequency properties of heterostructures based on bismuth selenide upon bipolar resistive switching: Experiments and numerical simulation

The effect applied voltage frequency has on bipolar resistive switching in microcontact type heterostructures based on thin films and single crystals of bismuth selenide is studied both experimentally and via numerical simulation.

Resistive switching and diode properties of mesoscopic niobium oxide-based structures

The bipolar effects of resistive switching (BRS) in mesoscopic heterostrucures based on amorphous and crystalline niobium oxide films are considered. The BRS effect is more pronounced in the structures based on multiphase nanocrystalline niobium oxide films. It is shown that the threshold frequency for observing the BRS effect is of the order of 104 Hz. Switching is controlled via oxygen electrodiffusion to vacancies as the doping level of the contact area and the resistive properties of the heterocontact change.