The metal–insulator–metal sandwich structures with the end surface of the insulator film (insulating slit) open to the gas environment were manufactured using thin-film technology. Electroforming, which consists of applying voltage according to a specific algorithm, causes the formation of conductive phase particles due to the destruction of organic molecules adsorbed on the open surface of the insulator by electron impact during the electric current flow. The accumulation of particles leads to the growth of a linked conductive cluster (a conductive carbon medium) and the formation of a conductive nanostructure with the memristor properties in the insulating slit. The practical use of such structures is limited by the low efficiency of electroforming: relatively long process times (on the order of several seconds) and an increased probability of electrical breakdown of the structure. Several ways to improve the efficiency of the electroforming process are presented. Firstly, the use of the correct voltage polarity for the open TiN–SiO2–W sandwich structure, where W should be the anode, which sharply reduces the probability of breakdown. Secondly, the use of two-stage electroforming: first, the formation of conductive channels in an “oil-free” vacuum after annealing in it, when the voltage can be applied in parallel to a large number of structures, and then in an “oil” vacuum containing organic molecules at significantly lower voltages and exposures. Thirdly, replacing the tungsten anode with a molybdenum one, which, while maintaining the advantages of tungsten, leads to an increase in the initial conductivity of the open sandwich structure (TiN–SiO2–Mo) by several orders of magnitude, and, therefore, to an acceleration of the electroforming process and a decrease in the applied voltages.

The processes of electroforming and functioning in a vacuum of memristors (elements of non-volatile electrically reprogrammable memory) based on open TiN–SiO2–Mo sandwich structures were studied. The experimental results showed that, firstly, these structures with a top molybdenum electrode are characterized by higher initial conductivity values than the previously studied TiN–SiO2–W structures. Secondly, for structures with Mo it turned out to be possible to reduce the electroforming voltage to values of 6–8 V, which is almost two times lower than for structures with W under the same experimental conditions. This increases the reliability of the functioning of memory elements, minimizing the likelihood of breakdown. Experiments with preliminary thermal annealing of open TiN–SiO2–Mo sandwich structures in an oil-free vacuum showed that the structures retained high initial conductivity, but did not undergo full electroforming. Based on the results obtained, a mechanism for the appearance of high built-in conductivity for open TiN–SiO2–Mo sandwich structures was proposed, which is based on the transfer of molybdenum atoms through the etchant to the open edge of SiO2 during its fabrication.

Memristors (elements of nonvolatile electrically reprogrammable memory) based on electroformed open sandwich-metal–dielectric–metal (MDM) structures are fabricated using thin-film technology. Studies of the electroforming process and the features of the current–voltage characteristics (CVCs) after it was carried out for structures with various electrode materials showed that in the case of a tungsten anode, it was possible to minimize the probability of electrical breakdown during electroforming and subsequent operation of the memory elements. This is valid for any position of the anode in the MDM structure: both upper and lower. However, it is experimentally shown that tungsten is not the optimal material. The production of the anode from molybdenum retains all the advantages of the design with tungsten, and in addition, it leads to a noticeable decrease in the electroforming voltage, which can increase the reliability of this process. The results obtained can be used to optimize the design of the memory element.

Elements of nonvolatile electrically reprogrammable memory, in which information is encoded by the value of resistance (memristors), based on electroformed open sandwich TiN–SiO2–W structures are made using thin-film technology. A significant effect of the presence of organic molecules in the insulating gap of open sandwich metal-dielectric-metal (MDM) structures on the nature of the process of their electroformation is shown. Removal of organic matter by annealing in an oil-free vacuum followed by electroformation results in only its first stage, i.e., the formation of a future conducting nanostructure nucleus. The second stage, the accumulation of particles of the conductive phase and the formation of a conductive medium, is absent, which manifests itself in low currents through the structure. At the same time, the second stage of electroformation is easily performed after placing the annealed structures in an oil vacuum, which ensures the flow of organic molecules to the surface of the insulating gap. The results obtained mean that the carbonaceous conducting medium formed from organic molecules plays a decisive role in the electrospinning process of such structures. A new method of electroformation is proposed, which makes it possible to practically exclude breakdowns of structures with a sharp increase in current, which increases the efficiency of this operation.

A study of the optical-reflection spectra (250–2500 nm) for the surface of lead sulfide crystals in the initial state and after the formation of a homogeneous ensemble of nanostructures is conducted. Single crystals of PbS are grown using the vertical-zone-melting method, with the [100] orientation along the growth axis. Surface nanostructuring is realized in a reactor of high-density argon plasma with a low-pressure high-frequency inductive discharge (13.56 МHz) at the ion energy ~200 eV. The uniform array of stepped lead sulfide nanostructures formed due to plasma treatment is up to 140 nm in height, with cruciform bases having ❬100❭-oriented lateral orthogonal elements 20–60 nm long. It is found that the specular-reflection- and diffuse-reflection spectra for the initial surface of the (100) PbS crystals and for that nanostructured in argon plasma differ significantly. Using the Kubelka–Munk theory of diffuse reflection and the Kumar theory of specular reflection, the band-gap value for the nanostructured surface of (100) PbS crystals is determined as 3.45–3.47 eV, exceeding the value for the initial surface of lead sulfide ~0.4 eV.

The electrical resistivity ρ of cobalt films with a thickness of 10 to 55 nm deposited in different modes of magnetron sputtering on SiO2/Si wafers with their subsequent ion-plasma treatment is investigated. Co films 42 nm thick with minimum ρ of 9.8 µΩ cm, comparable to ρ of a bulk metal, are obtained at a temperature of 600 K. Treating the Co film surface in dense argon plasma with an energy of ions of about 20 eV at room temperature leads to an increase in resistivity, while, at Т ~ 500 K, both a decrease and an increase in ρ are observed. Such a change in resistivity is due to the combined action of ion bombardment and temperature. The mechanism of action of the ion-plasma treatment on the electrical conductivity of the Co film is discussed.

The object of research are samples of nonvolatile electrically alterable memory elements (memristors) based on TiN–TiO2–SiO2–W open “sandwich” structures, in which conductive nanostructures with electrically alterable characteristics are formed by the electroformation. The effect of the oxygen pressure and the electroformation conditions on the switching of the memory element is investigated. With the new experimental material, the earlier established character of the dependence of the oxygen threshold pressure (Pth) on the limiting current of switching (Ilim) for the pulse switching on of a memory element is confirmed. A shift in the Pth(Ilim) curve for different electroformation conditions, which can be explained by the corresponding change in the size of the conductive nanostructure, is demonstrated. Based on the obtained experimental data, changes in the size and specific surface resistance of the material of the conductive medium with varying limiting current of the electroformation Ilimf are estimated, which reveals an increase in the compactness of the nanostructure with a decreasing current. The earlier proposed mechanisms of the processes are clarified. A well-grounded method of the choice of the conditions of the electroformation for open sandwich structures is devised.

In this work, we present results of a study of low-energy (Е i < 200 eV) sputtering of Co and Mo nanometer thin films in high-density argon plasma of a low-pressure radio-frequency inductive discharge with a controlled incident ion energy and ion current density onto the sample. The average ion energy was determined by the negative self-bias potential, which arises when the RF bias power is applied to the substrate. The ion current density was determined from the ratio of the increments in the RF bias power and the self-bias potential. The sputtering rate was determined in situ by a refractometric method from a sharp change in the intensity of a reflected laser beam signal at the moment of a removal of a metal film. Precise control of sputtering made it possible to detect a formation of nanoscale structures at a stage near the end of sputtering of metal films. The experimentally determined sputtering yields of Co and Mo were in agreement with the results of semiempirical calculations. We demonstrate that for ion-plasma sputtering, removal of Co and Mo atoms occurs at ion energy lower than the sputtering threshold.

Samples of nonvolatile electrically reprogrammable memory elements (memristors) based on electroformed TiN–TiO 2 –SiO 2 –W open sandwich structures, made using thin-film technology, are studied. A technique is developed and experimental studies are performed of the effect of oxygen pressure over the surface of the insulating gap of structures and the current limiting mode during the action of a switching pulse from a low to a highly conductive state on the characteristics of memory elements. The existence of a threshold value of oxygen pressure at which switching stops and its dependence on the value of the limiting current are shown. An interpretation of the experimental results based on the ideas developed on the mechanisms of the processes of the formation and disappearance of particles of the conducting phase in the insulating gap of an electroformed structure is presented.

In this work, the impact of the plasma treatment, during the formation of nanostructure arrays on the surface of the Cu(In,Ga)Se2 films on glass substrates, on the conductivity of the films both in the lateral direction and in the direction normal to the substrate surface was studied. The initial Cu(In,Ga)Se2 films with the Ga/(In + Ga) ratio in the range of 0.03–0.12 were obtained by thermal selenization process of stacked metallic precursors and by co-evaporation of all elements from various sources. The plasma treatment was carried out in a high-density low-pressure RF inductively coupled plasma reactor in argon plasma. The average ion energy was 200 eV, the processing time was 60 s. It is shown that the processes of the plasma nanostructuring of the Cu(In,Ga)Se2 film surface lead to the formation of a thin modified near-surface layer with a resistivity of 2–3 orders of magnitude less than for the bulk of the film.

In this work we report a new approach to the fabrication of metallic nanowire and nanonet structures on a-Si/SiO2/Si substrates by combine plasma etching processes. For the formation of Pt nanostmctures we used a controlled two-step plasma etching in C4F8/Ar and SF6 plasma, which resulted in a self-formation of fluorocarbon nanowires and nanonets. Then, we used these nanostructures as nanoscale templates for 10 nm thin metallic nanowires, which were obtained with magnetron Pt film deposition, Ar plasma sputtering and Pt redeposition.

In this work, we report a novel approach to the surface nanostructuring of lead tin telluride films using inductively coupled argon plasma treatment with the average ion energy of 200 eV and the duration of 20–60 s. The nanostructuring was carried out on the plasma treated surface of epitaxial single-crystal Pb1−xSnxTe films grown on BaF2(111) substrates using molecular beam epitaxy. The plasma treatment of the surface of the Pb1−xSnxTe films with the low and medium Sn content (x = 0–0.6) resulted in the formation of the arrays of ‘capped’ conical nanostructures with the height up to 420 nm, depending on the Sn content and treatment duration, and the surface density of ∼109 cm−2. The plasma treatment of the surface of the films with the high Sn content (x = 0.8–1) yielded the formation of a second group of flat nanostructures without ‘caps’, which had necklace-like rings consisting of multiple nanodroplets around their rims. Using transmission electron microscopy, we show that the quasi-spherical droplet ‘caps’ of the nanostructures consist of Pb ‘wrapped’ in Sn. We explain the physical mechanism of the observed plasma-assisted nanostructure self-formation in the framework of the multi-stage model including physical sputtering, redeposition, vapour-liquid-solid mechanism and micromasking mechanism.

Modification of indium sulfide (In2S3) film surface was performed by the treatment in high-density low-pressure inductively coupled argon plasma. The films with thickness of 500–800[Formula: see text]nm were fabricated on glass substrates by the thermal evaporation method and subsequent annealing in sulfur ambience. The plasma treatment of as-grown and annealed films was carried out with argon ions having the energy of 25–200[Formula: see text]eV. Nanostructuring of the film surface took place resulting in the formation of arrays of nanosized indium droplets.

In this work we have manufactured and studied memristors based on TiN-TiO2-SiO2-W open sandwich structures on Si substrates. We have built an experimental setup and developed a technique of the memristor resistive switching investigations in the controlled oxygen atmosphere within the pressure range of 0.0001–750 Torr. The resistive switching of the studied memory elements was carried out using voltage pulses with varying limitation current and depending on the oxygen pressure. As a result, we have found that the memory element resistive switching to the highconductivity “ON” state takes place below a certain threshold oxygen pressure, which has a non-trivial dependence on the limitation current.

We report on surface nanostructuring of Cu(In,Ga)Se2(CIGS) films using inductively coupled argon plasma treatment with the ion energy of 25–30[Formula: see text]eV within 30–120[Formula: see text]s. The films were fabricated on glass substrates using the selenization method and had a polycrystalline structure. We demonstrate that the plasma treatment results in the formation of tip-shaped nanostructure arrays with the geometrical parameters controlled by the treatment duration. The features of the surface nanostructuring using low energy ions are discussed.

In this work, we report a technique of the self-formation of a nanonet of fluorinated carbon nanowires on the Si surface using a combined etching in fluorine-containing C4F8/Ar and SF6 plasmas. Using scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy, we show that after the etching of Si in the C4F8/Ar plasma, a fluorinated carbon film of nanometer-scale thickness is formed on its surface and its formation accelerates at elevated temperatures. After a subsequent short-term etching in the SF6 plasma, the film is modified into a nanonet of self-formed fluorinated carbon nanowires.