CoCrFeNiTi high-entropy alloy (HEA) thin films were prepared on Si/SiO2 substrate by DC magnetron sputtering from one target of Co0.22Cr0.23Fe0.29Ni0.2Ti0.06 composition. The influence of sputtering time and power on the morphology, structure, chemical composition, resistivity, and temperature coefficient of resistance (TCR) has been studied. The thin films of the CoCrFeNiTi alloy exhibit a wide range of properties that can be tailored by adjusting the deposition parameters. The films demonstrate tunable TCR. The best TCR of 2.7 +/- 0.8 ppm/degrees C has been achieved. In addition, a head-to-head comparison with state-of-the-art thin-film resistor materials (NiCr, TaN, and HEA analogues) is presented for the first time. The study of the thermoelectric properties of the obtained films revealed a highest power factor (PF) value of similar to 0.015 mW/(m degrees C-2) and a linear behavior of PF increase in the range from -196 to 200 degrees C.

The work performed studies of Al–Ti–Si and Al–Ti–TiOx–Si structures with an n-TiOx/p–Si heterojunction. The TiOx layer was formed using the atomic layer deposition method; its thickness was 5 nm. To study the layers and composition of the structures, methods of electron microscopy, Auger spectroscopy, and Raman scattering were used. Much attention is paid to the study of electrical characteristics. It was found that the Al–Ti–Si structure is a Schottky diode, there is no minority carrier current in it, and the current–voltage characteristics are described by classical models. In the Al–Ti–TiOx–Si heterostructure, titanium oxide has n-type conductivity and is an injector of electrons into p-Si, which leads to the appearance of recombination currents in the space charge region, which lies entirely in silicon. When reverse biased, the titanium oxide layer acts as a conductor of electrons and contributes to the development of tunnel generation currents.

Magnetic quantum oscillations (MQO) of Hall coefficient are measured in rare-earth tritelluride TmTe$_{3}$ and shown to be much stronger and persist to higher temperature than the Shubnikov oscillations. It is general for MQO in strongly anisotropic metals, and the combined measurements of Hall and diagonal magnetoresistance provide useful informations about the electronic structure. The ratio of their MQO amplitudes depends linearly on magnetic field, and its slope gives a simple and accurate measurement tool of the electron mean free time and its temperature dependence.

Miniaturization of devices based on one-dimensional semiconductor nanocrystals is of high importance for high-frequency applications, photonics, and various sensors. Zinc oxide, one of the materials actively studied for such purposes, can be obtained by several technologies. Among them, chemical vapor deposition is distinguished by a low concentration of defects in the resulting structures. The aim of this work was to fabricate a test device on a single ZnO nanocrystal by means of nanomanipulation and to study its spectral response in the range from near-IR to UV. Since one of the promising applications of ZnO is UV sensors, the task was to test the selectivity of the response to the wavelength range below 400 nm.

An optical security element containing an area of random rough relief is proposed. It combines the low cost of mass replication inherent in traditional security holograms with the impossibility of holographic copying, when the wave restored by the hologram is rewritten as a copy of this hologram. The proposed optical element is also protected from contact and photographic copying. Laboratory samples of optical elements were obtained by taking replicas of a rough surface. Identification of the authenticity of optical elements was demonstrated by calculating the cross-correlation of speckle patterns produced by coherent light scattered off different replicas. It is assumed that the proposed security elements can be mass-produced on standard equipment for embossing security holograms.

AbstractTopological insulator nanostructures became an essential platform for studying novel fundamental effects emerging at the nanoscale. However, conventional nanopatterning techniques, based on electron beam lithography and reactive ion etching of films, have inherent limitations of edge precision, resolution, and modification of surface properties, all of which are critical factors for topological insulator materials. In this study, an alternative approach for the fabrication of ultrathin Bi2Se3 nanoribbons is introduced by utilizing a diamond tip of an atomic force microscope (AFM) to cut atomically thin exfoliated films. This study includes an investigation of the magnetotransport properties of ultrathin Bi2Se3 topological insulator nanoribbons with controlled cross‐sections at ultra‐low 14 mK) temperatures. Current‐dependent magnetoresistance oscillations are observed with the weak antilocalization effect, confirming the coherent propagation of 2D electrons around the nanoribbon surface's perimeter and the robustness of topologically protected surface states. In contrast to conventional lithography methods, this approach does not require a highly controlled clean room environment and can be executed under ambient conditions. Importantly, this method facilitates the precise patterning and can be applied to a wide range of 2D materials.

This paper presents the results of experimental studies of the cross section of the interfaces of the SrIrO3/La0.7Sr0.3MnO3 and Pt/La0.7Sr0.3MnO3, heterostructures, in which, upon excitation of ferromagnetic resonance in a La0.7Sr0.3MnO3 film, a spin current arises that flows through the interface in structure. Epitaxial growth of thin films of strontium iridate SrIrO3 and manganite La0.7Sr0.3MnO3 on a (110)NdGaO3 single-crystal substrate was carried out using magnetron sputtering at a high temperature in a mixture of argon and oxygen gases. The spin mixing conductance, which determines the amplitude of the spin current and generally has real Re g(up arrow down arrow) and imaginary Im g(up arrow down arrow) parts, was determined from the frequency dependence of the FMR spectrum of the La0.7Sr0.3MnO3 film and the heterostructures. It is shown that the Im g(up arrow down arrow) quantity can play an important role in determining the spin Hall angle (theta(SH)) from the angular dependence of the spin magnetoresistance. For the SrIrO3/La0.7Sr0.3MnO3 heterostructures, theta(SH) turns out to be significantly higher (almost an order of magnitude) than that for the Pt/La0.7Sr0.3MnO3 heterostructure.

Individual nanorods of ZnO are promising objects for optical and chemical sensing. We fabricate prototypes of UV and bionanosensors using a 3D nano-manipulation system from the nanorods synthesised by chemical vapour deposition (CVD). For the first time, we characterize the spectral response of individual ZnO nanorod to the UV-vis light, and we show its selective sensitivity to the UV range. We show that the liquid-gated device based on ZnO nanorod can be used as a bio-sensor, for example, for detecting hypoxanthine in pork meat.

The evolution of Al-Zn-Mg-Cu alloy microstructure during high pressure torsion at room temperature and subsequent low-temperature superplastic deformation is studied. The formation of a nanostructured state in Al-ZnMg-Cu alloy made it possible to implement a superplasticity (SP) effect at 170 degrees C and a strain rate of 5 x 10-4 s- 1. The deformation relief of the gauge part of an Al-Zn-Mg-Cu alloy sample at the stage of steady-state SP flow is analyzed. Low-temperature superplastic deformation is stated to take place due to grain boundary sliding. High formability of nanostructured alloy under biaxial tension at a temperature of 170 degrees C is recorded.

The measurements of electronic transport including the dynamic properties of the charge density wave (CDW) in the quasi-two-dimensional compound HoTe 3 have been performed. The effects of the slow relaxation of the nonequilibrium state of the CDW during isothermal exposure in the zero current mode, previously observed in TbTe 3 , have been discovered and studied. A significant increase in the exposure time made it possible to clearly demonstrate that the relaxation is logarithmic. Relaxation features were studied in different temperature and time ranges. The data obtained indicate the glassy behavior of the CDW pinning centers in rare-earth tritellurides.

Моделируется катастрофическая деградация эмиссионных катодов на основе углеродных нанотрубок, которая происходит из-за разрушения нанотрубки в дефектной области в результате перегрева. Модель учитывает разогрев нанотрубки путем выделения тепла Джоуля, а также радиационное излучение и охлаждение вследствие эффекта Нотингема, заключающегося в уменьшении температуры эмитирующего конца за счет энергии, уносимой потоком эмитированных электронов. Предложенная модель сравнивается с экспериментом по деградации одиночной нанотрубки. Эксперимент подтверждает катастрофическое разрушение и показывает, что разрушению способствует возникновение термоэлектронной эмиссии, которая вызывает быстрый рост тока и, соответственно, температуры дефектной области нанотрубки. Ключевые слова: автоэлектронные эмиттеры, деградация, разогрев нанотрубки, дефекты, катастрофическое разрушение.

Diodes of type Metal-Dielectric 1-Dielectric 2-Metal are promising for use in devices paired with antennas-rectennas. To create diodes with the characteristics required for operation, it is necessary to understand the mechanisms of current transport in both dielectrics and their contacts with metals. To solve this problem, it is necessary to develop an algorithm for dividing the general current-voltage characteristic into characteristics of individual contacts, the analysis of which will also allow us to investigate the problems of the properties of defects in the dielectrics that make up the diode. In this paper, the solution of the above problems is presented on the example of the Al-Al2O3-Ta2O5-Ni diode. The authors showed how one can divide the current-voltage characteristic into components, calculate potential barriers at the boundaries of metals with contacting dielectrics, and determine the concentration and energy characteristics of structural defects in dielectrics.

Solid-state photon emitters at room temperature appear to be promising candidates for a variety of nanophotonic applications. In this regard, coupling photon emitters with various optical cavities providing pronounced directivity, high photoexcitation and emission rates is extremely desirable. Here, we introduce the novel concept of deterministically coupling color centers in nanodiamonds (NDs) with gold nanopits. We show that in this case, emission of silicon-vacancy (SiV − ) centers at the zero-phonon line can exceed that of a ND on a gold surface by a factor of 62. The obtained results reveal an effective pumping of the SiV-centers in NDs along with the active switching of the SiV-centers from the dark to the bright state by plasmon mode that opens the way to design controllable resonance systems with diamond-based photonic emitters.

High-entropy alloys are promising materials for novel thin-film resistors since they have high resistivity and a low-temperature coefficient of resistivity (TCR). In this work, a new high-entropy thin-film CoCrFeNiTix was deposited on a Si/SiO2 substrate by means of magnetron sputtering of the multi-component target produced by hot pressing of the powder mixture. The samples possessed a thickness of 130–230 nm and an amorphous atomic structure with nanocrystallite traces. This structure persisted after being annealed up to 400 °C, which was confirmed using X-ray and electron diffraction. The film had a single-phase structure with a smooth surface and a uniform distribution of all elements. The obtained film served for microresistor elaboration, which was produced using the lithography technique and tested in a temperature range from −60 °C up to 200 °C. Resistivity at room temperature was estimated as 2.37 μOhm·m. The results have demonstrated that TCR depends on temperature according to the simple linear law in a range from −60 °C up to 130 °C, changing its value from −78 ppm/°C at low temperatures to −6.6 ppm/°C at 130 °C. Such characteristics show the possibility of using these high-entropy alloy films for resistive elements in contemporary and future micro-electronic devices.

The catastrophic degradation of emission cathodes based on carbon nanotubes is simulated, which occurs due to the destruction of the nanotube in the defective region as a result of overheating. The model takes into account the heating of the nanotube by releasing Joule heat, as well as radiation and cooling due to the Notingham effect, which consists in reducing the temperature of the emitting end due to the energy carried away by the flow of emitted electrons. The proposed model is compared with an experiment on the degradation of a single nanotube. The experiment confirms the catastrophic destruction and shows that the destruction is facilitated by the occurrence of thermoelectronic emission, which causes a rapid increase in the current and, accordingly, the temperature of the defective region of the nanotube. Keywords: field emitters, degradation, nanotube heating, defects, catastrophic destruction.

Heterogeneous superconductivity onset is a common phenomenon in high-Tc superconductors of both the cuprate and iron-based families. It is manifested by a fairly wide transition from the metallic to zero-resistance states. Usually, in these strongly anisotropic materials, superconductivity (SC) first appears as isolated domains. This leads to anisotropic excess conductivity above Tc, and the transport measurements provide valuable information about the SC domain structure deep within the sample. In bulk samples, this anisotropic SC onset gives an approximate average shape of SC grains, while in thin samples, it also indicates the average size of SC grains. In this work, both interlayer and intralayer resistivity were measured as a function of temperature in FeSe samples of various thicknesses. To measure the interlayer resistivity, FeSe mesa structures oriented across the layers were fabricated using FIB. As the sample thickness decreases, a significant increase in superconducting transition temperature Tc is observed: Tc raises from 8 K in bulk material to 12 K in microbridges of thickness ∼40 nm. We applied analytical and numerical calculations to analyze these and earlier data and find the aspect ratio and size of the SC domains in FeSe consistent with our resistivity and diamagnetic response measurements. We propose a simple and fairly accurate method for estimating the aspect ratio of SC domains from Tc anisotropy in samples of various small thicknesses. The relationship between nematic and superconducting domains in FeSe is discussed. We also generalize the analytical formulas for conductivity in heterogeneous anisotropic superconductors to the case of elongated SC domains of two perpendicular orientations with equal volume fractions, corresponding to the nematic domain structure in various Fe-based superconductors.

The article is devoted to solving urgent problems of nanotechnology and physics of nanostructures aimed at developing highly sensitive bionanosensors designed to solve difficult problems of diagnosing biological agents, in particular viruses. The high sensitivity of bionanosensors of biological molecules up to attomolar levels is achieved due to the fact that field-effect nanotransistors have a sensitive element in the form of a nanowire, the transverse size of which is comparable to the size of a bionanoagent, for example, a virus. Taking into account the fact that semiconductor nanowires are an extremely technologically advanced and cheap object, the wide application of such nanosensors based on field-effect transistors is hindered by the lack of only the technology for their manufacture. We have improved the technology of mechanical nanoassembly of structures such as field-effect transistors from suspended semiconductor nanowires. The selection of materials was carried out, and the technology for manufacturing nanostructures based on semiconductor nanowires was developed.

Nanosecond lasers have recently been widely involved in human activity. However, high-intensity laser radiation can cause severe damage to organs of vision and expensive photonic devices. Radiation in the near UV range is especially dangerous for human eyes, since it is strongly absorbed by biological media and is also invisible, i.e., the reaction time of the eye to such radiation is much lower than that of visible light. Passive limiters have high transmission (>70%) at a low light intensity and begin to “darken” only when the threshold value of the laser radiation intensity is reached. In this work, we studied liquid nanodispersed nonlinear optical limiters based on hybrids of single-walled carbon nanotubes (SWCNTs) with metal-free tetra(hydroxy)phthalocyanine (OH)4PcHH). The value of the hydrodynamic radius of separate particles after (OH)4PcHH binding increased from 288 ± 55 nm to 350 ± 60 nm, which confirms the attachment of phthalocyanine complexes to nanotubes. The third harmonic of a Nd:YAG nanosecond laser (355 nm, 20 ns) was used to study the nonlinear optical response. Based on a Z-scan with open-aperture and input-output dependence curves, third-order nonlinear optical absorption coefficients of 149, 236, and 229 cm/GW were obtained for dispersions of composites of SWCNTs and (OH)4PcHH in water, dimethylformamide (DMF), and dimethylsulfoxide (DMSO), respectively. Threshold values did not exceed 100 mJ/cm2. The Z-scan showed a gradual decrease in the duration of the laser pulse by 53%; however, near the focus, there was a sharp increase in the duration of the transmitted pulse, reaching a value of 29 ns in z = 0. This phenomenon confirms the occurrence of reverse saturable absorption in the investigated media and can be used in photonic devices to control the temporal characteristics of the signal. Thus, the possibility of protection of sensitive photonic devices and human eyes from nanosecond laser pulses in the near UV range by nanodispersed liquid media based on composites of SWCNTs with (OH)4PcHH has been discussed in this paper.

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the I-V characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the I-V characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim (F-N) function by one to three orders of magnitude. The I-V characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the I-V characteristics have distinct regions of negative differential conductivity.