This report presents the results of experimental investigations of cathode-grid structure based on CNTs. The experimental samples of field emission cathode-grid array based on vertical-aligned CNT with the cell of 1 μm diameter and with 5 μm pitch of microstructure are fabricated. The electron focusing system with a sheet CNT cathode with linear convergence 14, and with the beam current density of 78.4 A/cm2 has been designed in terms of experimental data of a current-voltage characteristic of the cathode.

This report presents the results of calculation of electron-optical system consisting of a sheet CNT field emission cathode with a microgrid spaced from the surface of the emitter at 100 microns. On the basis of experimental data, it has been designed electron-optical system with a sheet CNT cathode with linear convergence of 6,25, and with the beam current density of 4,46 A/cm2. The thickness of the beam in the interaction space is 0,16 mm. In this case, the simulation of the sheet electron beam, generated by electron gun has shown feasibility of obtaining of low-perveance flow with a small deformation in beam tunnel 0,3×0,8 at 25 mm slow-wave system length.

The field emission structure with thin conductive substrate of sufficient width and length with a double-sided emitting surface are tangent to the axis and coated with a nanoscale film of diamond-graphite clusters with pulling electrons grid is considered. The grid potential of the order of several (or tens) of volts generates a potential barrier. The electrons are emitted with approximately the Fermi velocity normal to the surfaces, and then their trajectories are rotated on 90 degrees using a focusing electrode and a longitudinal magnetic field. The electrostatic and magnetic focusing, ensuring the formation of wide and thin ribbon beam, are considered. The high current in wide band beam is achieved by increasing the width of the emitter and its longitudinal size (length).

A multibeam triode electron gun with a glassy carbon field-emission cathode that is intended for an O-type microwave amplifier is studied. The electric field strength and the current density at the microtips versus the distance to the center of a cell of the cathode–grid unit are calculated. Calculation data are compared with experimental results. It is shown that about 70% of the cathode current in each cell is accounted for by microtips arranged in a circumferential ring no wider than 20 μm. The field-emission current density inside the ring exceeds 40 A/cm2, and the current per microtip equals 43.1 μA.

This paper presents the results of experimental testing of diode electron guns with sheet and multiple electron beams based on thermionic minicathodes for TWT of terahertz frequency range. The results of study in pulse mode of impregnated thermionic blade cathode with linear dimensions 0.1×0.7 mm with a current density of 114 A/cm 2 are presented. A version of the five-beam electron gun is proposed with cylindrical minicathode with diameter of 0.25 mm, placing under the cells of control grid, achieved a current density of 85.5 A/cm 2 at grid voltage of 900–1000 V.

It is established that the field-electron emission characteristics of nanodiamond-graphite composite films deposited in nonequilibrium microwave plasma of low-pressure ethanol vapor depend on the deposition regime. The effect is explained in terms of the cluster model of deposited hydrogenated amorphous carbon (a-C:H) structure. By selecting a deposition regime so as to reduce the content of bound hydrogen in deposited carbon structures, it is possible to provide for a four- to sixfold decrease in the threshold field of field-electron emission as compared to that in a-C:H films obtained by other methods.

Tunneling (cold emission) through potential barriers of a complex shape in vacuum microelectronic diode and triode structures, including those with several electrodes, is theoretically investigated and I–V characteristics of these structures are obtained.

The self-organization effect of diamond nanocrystals in polymer-graphite and carbon films is detected. The carbon materials deposition was carried from ethanol vapors out at low pressure using a highly non-equilibrium microwave plasma. Deposition processes of carbon film structures (diamond, graphite, graphene) is defined. Deposition processes of nanocrystalline structures containing diamond and graphite phases in different volume ratios is identified. The solid film was obtained under different conditions of microwave plasma chemical synthesis. We investigated the electrical properties of the nanocrystalline carbon films and identified it's from various factors. Influence of diamond-graphite film deposition mode in non-equilibrium microwave plasma at low pressure on emission characteristics was established. This effect is justified using the cluster model of the structure of amorphous carbon. It was shown that the reduction of bound hydrogen in carbon structures leads to a decrease in the threshold electric field of emission from 20-30 V/m to 5 V/m. Reducing the operating voltage field emission can improve mechanical stability of the synthesized film diamond-graphite emitters. Current density emission at least 20 A/cm2 was obtained. Nanocrystalline carbon film materials can be used to create a variety of functional elements in micro- and nanoelectronics and photonics such as cold electron source for emission in vacuum devices, photonic devices, cathodoluminescent flat display, highly efficient white light sources. The obtained graphene carbon net structure (with a net size about 6 μm) may be used for the manufacture of large-area transparent electrode for solar cells and cathodoluminescent light sources

Analytic theory, numerical simulations, and experiments describing the compact multi-beams microwave split-cavity oscillator (MBSO), which operates with electron efficiency 45% at a frequency 18 Ghz with 0.8 A electron beam and a beam energy of 2.6 keV for a total output power approximately of 0.6 kW.

The principles of creation of TWT terahertz range are considered. Three electrodynamic models for slow-wave system (SWS) type comb to comb dielectric substrate in a rectangular screen have been obtained, and the calculated dispersion presented. The first model is based on the method of Green's functions and integral equations. The second model is based on the G.T. Markov formulas of excitation of a rectangular waveguide. The third model is based on the representation of SWS in the form of a microstrip line winding in the vertical plane and by using the dispersion equations based on the theory of long lines. The results for the dispersion and coupling resistance are presented.

Two electrodynamical models have been obtained and the dispersion has been calculated for the slow-wave system of metallic film comb type on dielectric comb substrate in the rectangular screen. The first model is based on the method of Green's functions and integral equations. The second model is based on G.T. Markov formulas of excitation of a rectangular waveguide. The proposed electrodynamic models have been applied for calculation of dispersion.

3D simulation of triode electron gun is performed with regards its structure of multiple-tip field emission cathode. The table of geometrical parameters of electron gun is defined (dg-a/Da=1.5-4.0; dg-a/dg-c=10-4-10-2) as well as the optimal potentials of grid with large scale holes where the electrical field is uniform. Thus the effect of electron lens of grid comes to a minimum and laminar electron flow is formed. The computer modeling of 19- beam electron gun with field emission glassy carbon cathode in magnetic field (N=106cm-2) and planar single-beam electron gun with CNT cathode (N=4·108cm-2) are carried out.

The tunneling (cold emission) across potential barriers of complex forms, including those for structures with multiple electrodes, is theoretically studied. The volt-ampere characteristics (VAC) of diode and triode structures of vacuum nanoelectronics are presented.

This paper presents the results of computer analysis of the sheet electron beams in a uniform and reverse magnetic field for low perveance electron-optical system based on thermionic cathode with a current density of 100 A/cm2 with a total length of 60-65 mm. Experimental studies in diode mode of dispenser thermionic cathode with dimensions of 0,1·0,7 mm are conducted and the feasibility of using one in vacuum microwave amplifiers of terahertz electronics is shown.

In this paper we present the computer analysis of magnetic focusing sheet electron beam with low perveance in the electron-optical systems with an electron gun based on thermionic cathode with a current density of 100 A/cm 2 at the distance of tunnel 25 mm. The results of experimental study in the diode mode of impregnated thermionic cathode with linear dimensions 0,1 × 0,7 mm have shown the feasibility of using this cathode in sub-THz vacuum amplifiers.

To determine the emission characteristics of diode structures we use multiple images relative to the plane of the anode and cathode. And for triode structures such procedure was made for cathode-grid and grid-anode regions. In order to avoid singularity we move these planes from the boundary of atomic layers for a half-period of the lattice a. The tunnel current density have been calculated for diode and triode structures which are with a good agreement with experiment.

We use the classic approach to get the quantum mechanical potential, and consider the field emission in a flat vacuum diode with size d and thin dielectric film with sufficient permittivity. Using the potential in the form of series of images we have calculated the forms of potential barriers at different film thicknesses and voltages at the anode. It can be explained by the fact that the film reduces the intensity of a field.

Results of the theoretical analysis of the multi-beam monotron oscillator K-band with split-cavity resonator are considered. The analysis of conditions of self-excitation in the small signal approximation is carried out. Numerical simulation of the oscillation processes build-up is performed. The results show the possibility of achieving an output power exceeding 600 W and an efficiency 45%.

The analysis of low-perveance electron beams with high density inside the drift space with a diameter lower than 0,3 mm for THz devices are presented in this work. In these studies the values of perveance of the beam are in range of (0,14÷0,35)10-7 A/V3/2. In this case the quantity of forming longitudinal low-perveance electron beams is determined by the influence of the initial thermal transverse velocities of electrons. Using the software Lorentz-1 the three-dimensional analysis of electron beams structure were carried out for the cases of focusing in electron optical system with magnetic-shielded cathode and cathode in uniform magnetic field. The result of electron optical system simulation with magnetic-shielded thermionic cathode is presented where ripple factor of electron beam drifted in magnetic field (1.2 T) of 0,13. The design of electron optical systems with array of field-emission cathode with the low-voltage grid control and with a density of cells N=107-108 cm-2 is also performed. Modeling of field emission was carried out in papers2, 3 by using the various technique of the initial transverse velocity. In our report we prefer the two-stage modeling as simulation the trajectories of the particles for one cathode-grid cell in magnetic field and assessment of the potential which corresponds to the maximum transverse velocity of electrons. For electron gun specifies the number of particles corresponds to the density of cells and the value of Umax. The calculation of the potential of transverse velocity was carried out according to the formula: Umax = 8,8-10-4(r0B)2 where r0-the radius of the cyclotron orbits (mm) defined for one cell in a magnetic field B (Gs). Based on the analysis we note that planar structures with micro-sized cathode have a significant drawback associated with a spread of the transverse velocity of the electrons, due to the lens effect in the holes of grid.

The explicit expressions (in the Vainshtein and Markov forms) are derived for the excitation of a cylindrical cavity with perfectly conducting walls and with impedance end faces. Excitation of a cylindrical cavity and a cylindrical waveguide with a preset nonuniform axial electron-beam current and a helical current with a variable pitch, which is excited by a concentrated voltage source and is loaded by a preset pointlike matched load, is considered. For the helical current, the integro-differential equation is formulated. The traveling-wave tube (TWT) is simulated in the preset beam current approximation taking into account the nonuniform winding of the spiral coil, nonuniform electron beam, and losses.