Nanocrystalline cobalt oxide Co₃O₄ has been prepared by precipitation and subsequent thermal decomposition of a carbonate precursor, and has been characterized in detail using XRD, transmission electron microscopy, and FTIR spectroscopy. The sensory characteristics of the material towards carbon monoxide in the concentration range 6.7–20 ppm have been examined in both dry and humid air. A sensor signal is achieved in dry air at sufficiently low temperatures T = 80–120 °C, but the increase in relative humidity results in the disappearance of sensor signal in this temperature range. At temperatures above 200 °C the inversion of the sensor signal in dry air was observed. In the temperature interval 180–200 °C the sensor signal toward CO is nearly the same at 0, 20 and 60% r.h. The obtained results are discussed in relation with the specific features of the adsorption of CO, oxygen, and water molecules on the surface of Co₃O₄. The independence of the sensor signal from the air humidity combined with a sufficiently short response time at a moderate operating temperature makes Co₃O₄ a very promising material for CO detection in conditions of variable humidity.

Resistive and capacitive switching in capacitor metal/nanocomposite/metal ($\mathrm{M}/\mathrm{NC}/\mathrm{M}$) structures based on $(\mathrm{Co}\text{−}\mathrm{Fe}\text{−}\mathrm{B}{)}_x({\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3{)}_{100-x}$ NC fabricated by ion-beam sputtering with metal content x ≈ 8–20 at. % is studied. The peculiarity of the structure synthesis was the use of increased oxygen content (approximately equal to 2 × ${10}^{-5}$ Torr) at the initial stage of the NC growth. The NC films, along with metal nanogranules of 3–6 nm in size, contained a large number of dispersed Co (Fe) atoms (up to approximately ${10}^{22}$ ${\mathrm{cm}}^{-3}$). Measurements are performed both in dc and ac (frequency range 5–13 MHz) regimes. When switching structures from high-resistance $(R_{\mathrm{off}})$ to low-resistance $(R_{\mathrm{on}})$ state, the effect of a strong increase in their capacity is found, which reaches 8 times at x ≈ 15 at. % and the resistance ratio $R_{\mathrm{off}}$:$R_{\mathrm{on}}$ ≈ 40. The effect is explained by the synergetic combination of the multifilamentary character of resistive switching (RS) and structural features of the samples associated, in particular, with the formation of a high-resistance and strongly polarizable ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ layer near the bottom electrode of the structures. The proposed model is confirmed by investigations of RS of two-layer nanoscale $\mathrm{M}/\mathrm{NC}/{\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3/\mathrm{M}$ structures as well as by studies of the magnetization of $\mathrm{M}/\mathrm{NC}/\mathrm{M}$ structures in the pristine state and after RS.

One-dimensional periodic surface structures were formed by femtosecond laser irradiation of amorphous hydrogenated silicon (a-Si:H) films. The a-Si:H laser processing conditions influence on the periodic relief formation as well as correlation of irradiated surfaces structural properties with their electrophysical properties were investigated. The surface structures with the period of 0.88 and 1.12 μm were fabricated at the laser wavelength of 1.25 μm and laser pulse number of 30 and 750, respectively. The orientation of the surface structure is defined by the laser polarization and depends on the concentration of nonequilibrium carriers excited by the femtosecond laser pulses in the near-surface region of the film, which affects a mode of the excited surface electromagnetic wave which is responsible for the periodic relief formation. Femtosecond laser irradiation increases the a-Si:H films conductivity by 3 to 4 orders of magnitude, up to 1.2 × 10⁻⁵ S∙cm, due to formation of Si nanocrystalline phase with the volume fraction from 17 to 28%. Dark conductivity and photoconductivity anisotropy, observed in the irradiated a-Si:H films is explained by a depolarizing effect inside periodic microscale relief, nonuniform crystalline Si phase distribution, as well as different carrier mobility and lifetime in plane of the studied samples along and perpendicular to the laser-induced periodic surface structures orientation, that was confirmed by the measured photoconductivity and absorption coefficient spectra.

This paper investigates the effect of alpha-particle irradiation on the memristive properties of titanium oxide-based structures. Multilayer TiOx/Ti structures were fabricated by magnetron sputtering and subjected to alpha-particle irradiation with a fluence of 2 × 1012 ions/cm2. Defect formation was modeled using the Monte Carlo method. The memristive characteristics of the structures were studied before and after bombardment. Ion bombardment was found to increase the number of stable resistive states by nearly three times, extend the number of switching cycles by 1.5 times, and significantly enhance the ROFF/RON ratio. This optimization of memristive parameters is attributed to the formation of locally created defects.

Ge₂Sb₂Te₅ (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment at the 1250 nm wavelength of 200 nm thin amorphous GST225 films on silicon oxide/silicon substrates. A raster treatment mode and photoexcited surface plasmon polariton generation allowed us to produce mutually orthogonal periodic structures, such as scanline tracks (the period is 120 ± 10 μm) and laser-induced gratings (the period is 1100 ± 50 nm), respectively. Alternating crystalline and amorphous phases at the irradiated surfaces were revealed according to Raman spectroscopy and optical microscopy studies for both types of structures. Such periodic modulation leads to artificial optical and electrophysical anisotropy. Reflectance spectra in the near infrared range differ for various polarizations of probing light, and this mainly results from the presence of laser-induced periodic surface structures. On the other hand, the scanline tracks cause strong conductivity anisotropy for dc measurements in the temperature range of 200–400 K. The obtained results are promising for designing new GST225-based memory devices in which anisotropy may promote increasing the information recording density.

In this work, thin films of hafnium oxide HfO_x obtained by electron beam deposition were crystallized by thermal annealing in air atmosphere. The relationship between the structural changes occurring as a result of annealing and the electrical properties of the films was determined. It was found that the formation of nanocrystals with a monoclinic structure in the studied films, occurring at annealing temperatures of 500°C and higher, is accompanied by a decrease in their specific conductivity by more than 6 times, which can be associated with a decrease in the number of oxygen vacancies as a result of structure ordering. It was also shown that the specific conductivity of all HfO_x films (pristine and annealed at different temperatures) has a strong dependence on temperature, described by the activation law with an activation energy from 0.86 to 0.93 eV. The obtained data can be used to improve the characteristics of memristive systems and other electronic devices based on hafnium oxide layers.