—The development of semiconductor integrated technology and the transition to nanometer resolution of the lithographic process has led to the development of semiconductor field-emission structures. However, the set of technologies for manufacturing field-emission devices has not, at present, been widely introduced into production and commercialization due to their short service life and insufficient operational stability. The work provides a comparative analysis of the significant results obtained to date on the development of semiconductor field-emission structures with a nanoscale conduction channel in order to assess the current state and prospects for further development of vacuum nanoelectronics. Technological and operational problems in the development of nanoscale field-emission triode structures using various semiconductor materials are analyzed. The progress achieved in the field of integrating nanoscale field-emission structures with standard complementary metal—oxide—semiconductot (CMOS) transistors is shown. Possible areas of the application of vacuum nanoelectronic structures are considered. The current tasks of this scientific field are described, as well as problems arising in the process of introducing the elemental base of vacuum nanoelectronics into the cycle of development and commercialization of vacuum IC technology.

Currently, the development of uncooled IR microbolometer arrays based on SOI structures attracts significant attention of researchers, due to their high speed and temperature sensitivity compared to other bolometric and thermocouple sensor elements operating in the IR wavelength spectrum.An important parameter of such SOIbased IR microbolometers is the useful area of the dielectric (SiO 2 ) membrane that absorbs IR radiation and its high thermal insulation, which requires technological optimization of the sacrificial layer (Si) etching modes through a matrix of holes (windows) in the SiO 2 membrane.In this work, TCAD simulation of the gas-phase etching of the sacrificial Si layer was carried out, taking into account both its thickness and the size of the windows.It was shown that a decrease in the window size from 120 to 80 μm 2 leads to a twofold decrease in the etching time (from 480 to 240 seconds) and provides an effective increase in the useful surface of the microbolometer sensing element, which is heated by IR radiation.The obtained results can be useful in the process of working out technological operations for the fabrication of IR microbolometer arrays based on SOI substrates.

The paper presents a multiparameter experimental study of the multi-tip field emitter based on the array of silicon pyramidal microstructures. Emitter was created using standard silicon microfabrication process. Sample measurement was performed using computerized method with online processing of the field emission data. Obtained experimental current-voltage characteristics demonstrate good agreement with the expected theoretical estimates of the field-emission current.

Prediction of electron field-emission current of nanoscale devices is of significant importance in the field of vacuum nanoelectronics. Nowadays, modified Fowler-Nordheim model (FN) being widely used to estimate electron field-emission current of various systems. Nevertheless, it was shown that experimental values of the emission current from nano-scale emitters can differ from such values obtained within F-N theory. Moreover, the F-N formalism is not entirely suitable for describing field emission from silicon nanostructures, where it is important to take into account the interaction of electrons with impurities, phonon scattering, temperature effects (Joule heating), and the penetration depth of the electric field in the semiconductor. For the accurate simulation of electron field emission in the case of nano-scale silicon tip, first-principle quantum-mechanical models based on Density Functional Theory (DFT) and Density Functional Perturbation Theory (DFPT) formalisms should be used. In this work, we calculated within first-principle approach the field-emission current in a system consisting of the silicon nanoscale tip (emitter) and collector of the same type, which are separated by a nanoscale vacuum gap. The calculations were performed using time-dependent perturbation theory for non-zero external electric field within the non-equilibrium Green functions (NEGF) formalism to describe the electron transport and inelastic scattering in the emitter, where pseudopotentials and Kohn-Sham equations are explored in a self-consistent manner. This theoretical approach can serve as an important step towards the consideration of field-electron emission process beyond the F-N theory to describe correctly field-emission experimental data at the nanoscale.

In this work, experimental samples of Mo-based planar diode and triode field emission structures with a 150 nm vacuum channel were fabricated by electron beam lithography and plasma-chemical etching. The experimental current-voltage characteristics of the fabricated samples were obtained by means of the experimental set-up for the measurements in the high-vacuum conditions consisting of scanning electron microscope/focused ion beam system and semiconductor device analyzer. The experimental current-voltage characteristic confirmed Fowler-Nordheim mechanism of the electron transport in the fabricated molybdenum field emission structures.

In field electron emission (FE) studies, the current/voltage or the macroscopic current-density/field characteristics of single tip or large area field emitters can be expressed in a nearly linear form using one of a small number of standard data-analysis plots. Usually, the chosen plot is a Fowler-Nordheim plot, a Murphy-Good plot or a Millikan-Lauritsen plot. The FE orthodoxy test can be applied to any of the three types of plots, to test the reasonability of the obtained experimental data. A difficulty of using the orthodoxy test is that there is no technical procedure or simple platform that can be used to apply the test to the experimental data. This report describes a simple web-tool that is designed to apply the FE orthodoxy test to any of these data-analysis plots, and then to use the test results to extract the emitter characterization parameters if the data passes the orthodoxy test. The web-tool is used by specifying the nature of the plot, the emitter‘s local work function, relevant system macroscopic parameters, and the coordinates of two “end-of-range“ points on a line fitted to the data-analysis plot. The web-tool simplifies the data processing related to FE studies and experiments by: determining the value of the pre-exponential voltage/field exponent κ for Murphy-Good plots; evaluating the scaled-field parameters in FE theory that correspond to the ends of the working range; determining the status of the tested data before publishing it; determining the status of the emitter or experiments. Hopefully, the web-tool can help to develop basic understanding of the different behaviors of emitters. INTRODUCTION In field electron emission (FE) theory, Fowler-Nordheim (FN), Murphy-Good (MG) and Millikan-Lauritsen (ML) data-analysis plots are methods for presenting measured current/voltage Im(Vm) or the macroscopic current-density/field JM(FM) characteristics of FE experiments in a nearly linear form. Advantages of using Murphy-Good plots are that they are predicted to be “very nearly straight“ [1], and that there are fewer correction factors in the mathematics of the data-analysis process. A web-tool has been developed that allows researchers to easily test and analyze experimental results by first applying the so-called orthodoxy test and then (if the test is passed) extracting characterization parameters for the emitter used. The three types of plots can be presented in the general form ln(Y⁄ Xκ) vs X-1. Here, Y is either the measured total emission current Im or the macroscopic current density JM, X is either the measured voltage Vm or the macroscopic electrostatic field intensity FM, and κ is the pre-exponential voltage exponent in the empirical FE equation Im= C(Vm) κ exp[–B/Vm]...(1), where B can be treated as a constant and C can often be approximated as a constant. In the expanded form of the Murphy-Good FE equation, κ is given by 2-(η ⁄ 6), where η is the scaling parameter for the Schottky-Nordheim (SN) barrier and is given by η(f)= bcS 2f-1/2, where b is the second FN constant, cS is the Schottky constant and f is the local work function [2]. Thus, κ=2 for FN plots, 0 for ML plots, and 2-(η ⁄ 6) for MG plots [2]. The field emission orthodoxy test is a quantitative test that can be applied to any of the data-analysis plots and to any geometrical emitter shape for which MG FE theory is an adequate approximation. The test is based on extracting values of a specific and important parameter in FE theory. This parameter is the characteristic scaled field fC= cS fFC= cS fzC Vm, where FC is the local electrostatic field at a characteristic location on the emitter surface (usually taken as its apex), and zC [Vm/FC] is the related characteristic voltage conversion length (VCL). The extracted fC-values are then compared to a set of internal analyzed historical data, taken from metal emitters between 1926 and 1972. These data provide the orthodoxy test criteria as listed in [3]. The test is an “engineering triage“ test and provides three results. (1) Pass: the data are reasonable. (2) Fail: the data are unreasonable, and the extracted parameters are likely to be spurious. (3) Inconclusive; the data need more study and analysis. If the orthodoxy test is passed, then the characterization parameters of the emitter can validly be extracted. Typically, these are: the formal emission area (for a Schottky-Nordheim barrier) Af SN, and the related formal area efficiency αf SN; the VCL zC, and the related characteristic field enhancement factor (FEF) γC [2]. METHODOLOGY The FE analysis web-tool [4] had been developed for the purpose of applying the orthodoxy test. It does this by making precise calculations for the parameter-extraction process from any of the three types of data-analysis plot. It is necessary to precisely calculate the values of the FE theory scaled parameters and (for MG plots) the κ value as defined in [1]. The main tool requires only the plot form, the assumed value of f, and the coordinates of the upper and lower limits for the line fitted to the data. To extract values for γC and αf SN, where relevant-usually only for large area field electron emitters (LAFEs)-further macroscopic system parameters are needed, namely a cathode-anode macroscopic distance dM (there are several types) and the macroscopic area AM of the LAFE. To test the performance of the web-tool, simulated currentvoltage data plots were generated, for each of the three types of plot, using the input parameter-values: f=4.65 eV, Af SN=100 nm2, zC=180 nm, dM=100 mm, AM=100 mm 2, with the tested range set to be 0.17≤fC≤0.43 (which is chosen to pass the orthodoxy test). RESULTS AND DISCUSSION The simulated data are presented in Figure 1. For the MG plot, the value of κ has been calculated using the formula given earlier, which yields κ=1.2398. With each of the plots, a line fitted to the plot would have slope Sfit and intercept ln(Rfit ) on the vertical (1000/Vm=0) axis. Both these values can in fact be obtained from the coordinates that correspond to the range of the fitted lines. The resulting values of Sfit and ln(Rfit ), as evaluated by the web-tool, are shown in Table 1. [Note that the Neper (Np) is the SI recognised unit of natural logarithmic difference, for amplitude-type quantities]. The range of fC-values extracted from each of the plots, using the relevant formula in [3], coincides with the chosen input range, thereby demonstrating consistency. Figure 1. Simulated data-analysis plots for the three plot types shown, for f= 4.65 eV, Af SN= 100 nm2, zC= 180 nm, and 0.17≤fC≤0.43. Table 1 also shows values of extracted characterization parameters, except that no reliable theory currently exists for extracting area-like quantities from a ML plot. All the data-analysis plots have “nearly straightline behavior“, but each plot is slightly curved in a different way. This leads to a noticeable variation and percentage error in the extracted values of the characterization parameters but does not significantly affect the results of the orthodoxy test. With this set of chosen data the FN plot appears to work slightly better than the MG plot, but our general impression is that for extracting area-like quantities the MG plot is expected to be more reliable and easier to use. CONCLUSIONS There is a need for a user-friendly tool that can apply the field emission orthodoxy test to experimental data, and (if appropriate) easily extract characterization parameters. Information of this kind is useful in the research and development of electron sources, in our case improved electron microscope sources and hybrid-design sources involving dielectric layers on metal point sources, but more generally sources based on large area field electron emitters. Our web-tool [4], now in its final stages of development, seeks to provide this facility, for all the forms of data-analysis plot commonly used. Notwithstanding this, our strong recommendation is that best engineering and scientific practice is to always plot the raw measured current/voltage data [5], to use a Murphy-Good plot rather than a Fowler-Nordheim plot, and to apply the orthodoxy test before attempting to extract characterization parameters. Table 1. The extraction results for each of the Figure 1 data-analysis plots. Figure 2. The web-tool form to apply the orthodoxy test to a LAFE sample. -45 -40 -35 -30 -25 -20 -15 -10 -5 0 0.0 0.5 1.0 1.5 2.0 2.5 ln (I m /V m κκ ) [ ln (A /V κκ ) ] 1000/Vm [V-1]

Currently, great interest of the scientific community is attracted to the creation of miniature and highly sensitive pressure sensors, which is associated with their demand in a wide range of applications: in tele - and biomedicine, the automotive and aerospace industry. In this work, we propose an original design of a novel sensor with a thermal method for measuring applied pressure based on the micromechanical deformation of a composite dielectric membrane located near a thermosensitive thin-film thermocouple, which was not considered previously. It was found that the proposed design of the pressure sensor with a membrane-based thermal principle of operation provides maximum sensitivity of about 25 mK/Pa in a wide range of measured pressures (from 0.1 Pa to 100 kPa), which can be effectively used in modern altimeters for aircraft and unmanned vehicle control systems.

An optimized design of an analog circuit for measuring the parameters of a MEMS (microelectro-mechanical system)-based thermoresistive flow-rate sensor is proposed, which combines both calorimetric and anemometric flow measurement modes. Fixing the sensor on a plastic wing tilted at a non-zero angle relative to the direction of gas flow in such a system makes it possible to measure the gas flow velocity in a wide range from 0.05 to 5 m/s with an error of 3 % and a relative standard deviation of 2 %. The use in the proposed circuit of platinum thermistors located on a thin-film dielectric membrane (SiO2/Si3N4/SiO2/Si3N4), which can serve both as heaters and sensitive resistors for temperature measurement increasing the output voltage by an order of magnitude, thereby reducing the noise that occurs when a weak signal is amplified. It has been experimentally shown that the calorimetric method is more suitable for measuring low flow velocities (from 0 to 1 m/s), while the anemometric one is better applicable for detecting higher flow velocities (more than 1 m/s). The rise in temperature of thermistors due to its Joule heating by direct current was measured both in air and in vacuum in the absence of the gas flow. It was found in the experiment that the in-plane thermal conductivity of the four-layer dielectric membrane used in the sensor varies from 2.61 W/(m.K) to the level of about 3.03 W/(m.K) with an increase in the heating power in the range from 0.6 to 4 W, respectively. (C) 2021 Elsevier B.V. All rights reserved.

Much attention in the development of portable X-ray tubes is paid to the fabrication of field emitter arrays as an electron source. First of all, this is due to the fact that such arrays of field emitters are capable of providing a high and uniform current density required to obtain a high intensity of X-ray radiation at the output, good stability of the X-ray tube operation over a long period of time, as well as a micrometer size of the focal spot for obtaining X-ray images with high resolution. One of the important aspects in the technology of the array nanofabrication is the analysis of the uniformity of the field enhancement factor and field emission current of each of the silicon emitter over the whole array, which is necessary for the stable operation of X-ray tubes (without reducing the number of active emission centres). In this work, we performed an analysis of the statistical dispersion of the field enhancement factor of the silicon field emitters in the fabricated array with a size of 300 x 300 and a distance of 3 μm between the array elements, where the maximum current from the array reaches values up to 393 μA. The results obtained can be used in the development of mobile microfocus X-ray sources.

Устройства вакуумной электроники зарекомендовали себя во многих технических отраслях. Для дальнейшего развития отрасли необходимо совершенствование методов изготовления автоэмиссионных (АЭ) структур. В работе представлена технология создания АЭ диодных и транзисторных структур на основе молибдена (Mo).

Разработана математическая модель чувствительного элемента теплового сенсора расхода газа для компактного газового хроматографа. Рассчитана зависимость температурного отклика терморезисторов чувствительного элемента от скорости протекания потока газовой смеси различного типа. Получен профиль распределения концентрации газа и температуры в месте локализации чувствительного элемента.

Предложена оригинальная концепция теплового датчика давления и проведен численный анализ его рабочих характеристик. Показано, что оптимальная конструкция датчика обеспечивает чувствительность до 4,4 мК/Па в широком диапазоне давлений (от 0,01 до 100 кПа).

The paper considers the features of evaluating the effective parameters of nanostructured field cathodes - the area of the field emission S eff and the field gain β eff . A variety of approaches to parameter estimates is shown. The dependence of these estimates on the magnitude of the applied electric voltage is shown by the example of a three-dimensional model of a carbon nanotube. The possibility of the experimentally estimation of individual emission sites using a computerized field projector is considered. A method for analyzing the current-voltage characteristics in Fowler-Nordheim coordinates (IVC-FN) with an interval estimate of the effective parameters is proposed.

A process flow for the creating of diode and triode field-emission needle-type and blade-type nanostructures is proposed. The created experimental samples were studied using scanning and transmission electron microscopy. Current-voltage characteristics of the created experimental samples of silicon field-emission structures are obtained. The results of this paper can be used to create field-emission nanostructures for development of high-frequency electronics in the GHz range.

Using atomic force microscopy (AFM), we experimentally examined the features of field-electron emission from a single point-type silicon cathode into a quasi-vacuum (air) medium. In the non-contact AFM operating mode, the current – voltage characteristics (CVCs) of a single cathode with a nanometer radius of curvature of the tip were measured at distances of 10 nm and 20 nm between the cathode tip and the top of the measuring probe. The electric field distribution was simulated both on the surface of the tip of a single cathode and on the surface of the tips of individual cathodes within the array, based on which a theoretical estimate of the field enhancement factor as a function of the cathode-probe distance was made. The field-enhancement factor calculated from the experimental CVCs in the Fowler-Nordheim coordinates is several orders of magnitude higher than its value obtained from theoretical calculations. Such a mismatch between the experimental data and the simulation results indicates the need to take into account additional quantum-size effects, which play an important role in the formation of the field-electron emission current in the nanoscale gap. In particular, deformation of the silicon emitter tip can occur at this scale due to the penetration of a strong electric field into its surface region, which, in turn, causes the distortion of the potential barrier at the interface with the quasi-vacuum medium.

Atomic force microscopy is employed in the experimental study of specific features of the field emission of electrons from a single silicon needle-type cathode to quasi-vacuum (air). Noncontact regime of the atomic force microscopy is used to measure the I – V characteristics of a single cathode with nanometer-scale tip radius at distances of 10 and 20 nm between the cathode tip and the measurement probe. Electric field distributions are simulated for both surface of the tip of a single cathode and tip surfaces of single cathodes in an array, and the results are used to theoretically estimate electric field enhancement versus cathode–probe distance. It is shown that the enhancement factor calculated from the experimental I – V characteristics in the Fowler–Nordheim coordinates is greater than the result of theoretical calculations by several orders of magnitude. This circumstance indicates that additional quantum dimensional effects that play an important role in the generation of the electron emission current in the nanoscale gap must be taken into account.

The technological prospects for the creation of a system of microfocus X-ray tubes with the use of silicon field emission of nanocathodes have been discussed. A numerical analysis of the field-emission current from a nanoscale semiconductor cathode regulated by voltage on a grid electrode has been carried out on the basis of which a scheme for controlling the elements of the matrix of field-emission cathode assemblies has been proposed. The current–voltage characteristics of silicon field emission nanocathodes have been measured. They are in good agreement with the theoretical estimates of the field-emission current. A full technological cycle of the development of elements of microfocus X-ray tubes (a set of field-emission cathode assemblies and a set of anode assemblies) has been performed. The results can be used to create systems of microfocus X-ray tubes for nanolithographic equipment of a new generation.

Full fabrication process of nanoscale vacuum channel and gate-all-around nanowire transistors at the 45, 32 and 22 nm technology nodes was simulated in Silvaco TCAD. Comparative analysis of operation modes was made on the basis of the obtained structures. It was shown that nanoscale gate-all-around transistor has sufficiently low power consumption while vacuum channel field effect transistor makes it possible to achieve performance that exceeds performance which can be obtained from the transistor with semiconductor channel. The combination of the above technologies can serve as approach to the creation of low-power and high-speed nanoscale vacuum devices using established complementary metal-oxide-semiconductor (CMOS) technology.

The reproducibility of complementary metal-oxide-semiconductor (CMOS) technology makes it very promising for creating commercially available vacuum emission micro/nanoelectronic devices. However, there are a number of challenges that occur with CMOS, including current hysteresis, transition to the generation of self-sustained plasma, and thermal melting of the cathode. These issues affect the process of field-electron emission and lead to instability and subsequent degradation of field-emission cathodes. More detailed study is needed in order to address these negative effects. In this study, an array of nanoscale silicon needle-type cathodes and a single blade-type cathode were placed in vacuum to characterize their field-emission properties. The hysteresis nature of the field-emission current and the smooth transition from field emission to the generation of self-sustained plasma in the interelectrode space were simultaneously observed. Based on these experimental results, the authors propose the possible origins and mechanisms underlying these two phenomena. It was theoretically found that at field-emission currents corresponding to the observed melting point of the silicon nanocathodes, the melting point of silicon is not reached, which indicates the need to take into account additional effects of field emission, such as sputtering of the anode material. The results are useful for developing field-emission nanodevices based on silicon CMOS technology.

Abstract The technological prospects for the creation of a system of microfocus X-ray tubes with the use of silicon field emission of nanocathodes have been discussed. A numerical analysis of the field-emission current from a nanoscale semiconductor cathode regulated by voltage on a grid electrode has been carried out on the basis of which a scheme for controlling the elements of the matrix of field-emission cathode assemblies has been proposed. The current–voltage characteristics of silicon field emission nanocathodes have been measured. They are in good agreement with the theoretical estimates of the field-emission current. A full technological cycle of the development of elements of microfocus X-ray tubes (a set of field-emission cathode assemblies and a set of anode assemblies) has been performed. The results can be used to create systems of microfocus X-ray tubes for nanolithographic equipment of a new generation.