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Vol 53, No 1 (2024)
ДИАГНОСТИКА
Analysis of Nonlinear Distortions of Dphemt Structures Based on a GaAs/InGaAs Compound with Double-Sided Delta-Doping
Abstract
The paper presents the results of studies of C–V characteristics of GaAs/In0.53Ga0.47As HEMT before and after neutron irradiation with a fluence of (6.3 ± 1.3) × 1014 cm–2. Based on the experimentally obtained characteristics, the effective electron distribution profiles of the structure were calculated before and after radiation impact. The effect of radiation defects on the δ-layers of the structure was analyzed.
3-7
Structuring of the Surface of Thin Carbon Films During Activation by Microsecond Current Pulses
Abstract
The influence of current activation by electric pulse breakdown on changes in surface morphology and emission characteristics of a field emission cathode made on the basis of carbon films obtained by deposition in a microwave gas discharge plasma was studied. Current activation of these films was carried out by applying voltage pulses of microsecond duration until an electrical breakdown occurred. It is shown that during activation, the morphology of the film surface in the breakdown region changes with the formation of a micro-sized emitting structure, which significantly improves the field emission characteristics of cathodes based on carbon films.
8-15
МОДЕЛИРОВАНИЕ
Modeling of Physical-Chemical and Electronic Properties of Lithium-Containing 4H—SiC and Binary Phases of the Si—C–Li System
Abstract
In the equilibrium model of the solid surface–adatom system, including a three-dimensional interfacial surface, changes in surface properties are considered, taking into account the chemical potential due to the action of surface tension. The relationship between chemical potential and electrochemical potential of the ith component in an electrochemical cell is analyzed. Using the density functional theory (DFT), the adsorption, electronic, and thermodynamic properties of 2 × 2 × 1 and 3 × 3 × 1 supercells of crystalline compounds AmBn, (, where n and m are stoichiometric coefficients) of the boundary binary systems of the ternary phase diagram of Si–C–Li are studied. The stability of phases AmBn and property calculations are carried out with the exchange-correlation functional within the framework of the generalized gradient approximation (GGA PBE). The parameters of the crystal structures of the compounds AmBn, the adsorption energy of the lithium adatom on a 4H–SiC substrate, the electronic structure, and the thermodynamic properties of supercells are calculated. The thermodynamically stable configurations of the 4H–SiC–Liads supercells having different locations Liads are determined. The DFT GGA PBE calculations of the enthalpy of formation of compounds AmBn are carried out in the ternary Si–C–Li system. Taking into account the changes in the Gibbs free energy in the solid-phase exchange reactions between binary compounds, equilibrium sections (connodes) in the concentration triangle of the Si–C–Li phase diagram are established. An isothermal section of the Si–C–Li phase diagram at 298 K is constructed. The patterns of diffusion processes that are related to the movement of particles on the surface layer of the 6H–SiC sample are analyzed. The activation energy of lithium diffusion in 6H–SiC is calculated from the Arrhenius type relation in two temperature ranges (769–973 K) and (1873–2673 K).
16-38
Modeling of the Electronic Properties of M-Doped Supercells (М = Zr, Nb) with a Monoclinic Structure For Lithium-Ion Batteries
Abstract
The T–x phase diagram of the quasi-binary system Li2O–TiO2 was refined and the isothermal cross section of the ternary Li–Ti–O system at 298 K was constructed. The equilibrium phase regions of Li–Ti–O in the solid state are determined with the participation of boundary binary oxides and four intermediate ternary compounds , , and . Using the density functional theory (DFT LSDA) method, the formation energies of the indicated ternary compounds of the Li2O–TiO2 system were calculated and the dependence of on the composition was plotted.
Ab initio modeling of supercells based on M-doped anode material based on the (LTO) compound with a monoclinic structure () was carried out. It has been shown that partial substitution of cations and oxygen in the m-LTO–M structure increases the efficiency of a lithium-ion battery (LIB) both by stabilizing the structure and by increasing the diffusion rate of . Due to the contribution of d-orbitals (Zr4+-4d, Nb3+-4d orbitals) to the exchange energy, partial polarization of electronic states occurs and the electronic conductivity of m-LTO–M increases. The formation of oxygen vacancies in the m-LTO–M crystal lattice, as in binary oxides, can create donor levels and improve the transport of and electrons.
M-doping of the m-LTO structure by replacing cations, in particular lithium, with Zr or Nb atoms noticeably reduces the band gap (Eg) of m-LTO–M supercells. In this case, in the m-LTO–M band structure, the Fermi level shifts to the conduction band and the band gap narrows. Decreasing the Eg value increases the electronic and lithium-ion conductivity of m-LTO–M supercells.
39-50
ПРИБОРЫ
Electron Transport in a Bipolar Transistor with a Superlattice in the Emitter
Abstract
A set of transfer and output current-voltage characteristics of a bipolar transistor with a short-period superlattice in the emitter region has been calculated. It is shown that the presence of a superlattice in the tr ansistor structure leads to the fo rmation of a negative differential conductivity region, which makes it possible to implement not only amplification, but also the generation and multiplication of high-frequency oscillations.
51-57
Research of Memristor Effect in Crossbar Architecture for Neuromorphic Artificial Intelligence Systems
Abstract
This article presents the results of experimental studies of structures formed on the basis of the crossbar architecture of memristor structures made of various materials. TiO2 was used as a working memristor layer. The following materials were used for the contact pads: Al, Ni, Cr, Mo, Ta, Ag. In the course of experimental studies, the optimal combination of materials for the formation of crossbar memristor structures was revealed, which in the future can be used in devices of neuromorphic artificial intelligence systems.
58-63
ТЕХНОЛОГИИ
Application of Spectral Ellipsometry for Dielectric, Metal and Semiconductor Films in Microelectronics Technology
Abstract
The article reviews model-based and model-free approaches to solving problems of spectral ellipsometry related to the measurement of thicknesses and optical parameters of thin layers of dielectrics, metals and semiconductors in microelectronics application. Model-based approaches employ a priori information about the dispersion relation in form of the Cauchy, Drude, Drude—Lorentz and Tautz—Lorentz. Model-free approaches can use any smooth multivariate functional dependence describing a smooth spectral curve. Also, machine learning can be used to implement the model-free approach, which is well suited for determining the thickness of multilayer structures and their optical characteristics and allows to significantly increase the speed of data processing.
64-74
Features of Electroforming and Functioning of Memristors Based on Open TiN–SiO2–Mo Sandwich Structures
Abstract
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.
75-84
Molecular Layering of an Additive Layer of Silicon Dioxide on Anodized Tantalum and Niobium Oxides
Abstract
The results of studying the processes of formation of nanolayers of silicon oxide by the method of molecular layering (atomic layer deposition) on the surface of films of tantalum and niobium oxides obtained by electrochemical oxidation of the corresponding metals are presented. A study of the electrical strength of metal-dielectric-metal (MDM) structures based on tantalum and niobium oxides showed that the introduction of an additive dielectric layer (SiO2) can significantly increase the electrical strength of these structures.
85-90
Parameters and Composition of Plasma in a Mixture of CF4 + H2 + Ar: Effect of the CF4/H2 Ratio
Abstract
A study of the electrophysical parameters of plasma and the kinetics of plasma-chemical processes in CF4 + H2 + Ar mixture by varying the CF4/H2 ratio were carried out. Using diagnostic methods and plasma modeling together, it was found that replacing tetrafluoromethane with hydrogen a) leads to a decrease in plasma density and an increase in electronegativity; and b) causes a disproportionately sharp drop in the concentration of fluorine atoms. The reason for the latter effect is an increase in the frequency of death of atoms in reactions of the form CHFx + F → CFx + HF, initiated by heterogeneous recombination according to the CFx + H → CHFx mechanism. A simultaneous increase in the concentration of polymer-forming radicals CHxFy (x + y < 3) indicates an increase in the polymerization load of the plasma on the surfaces in contact with it.
91-101
Interconnects Materials for Integrated Circuit Technology Below 5 Nm Node
Abstract
As the integrated circuits is scaled few problems appear at the lowest levels of interconnects — high resistance of copper lines and copper electromigration. High resistance is connected with the increasing contribution of the electron surface scattering and grain boundary scattering. Moreover, copper lines require barrier layers decreasing the cross-section of the copper part of the line. Also the resistance of copper to electromigration is insufficient for the technology node below 5nm. Therefore, it is necessary to look for alternative materials to replace copper, which will provide high resistance to electromigration and low resistance of the lines. The most promising candidates are Ru, Mo, Rh, Ir. The advantages and disadvantages of these materials are considered in this paper.
102-116