The paper discusses the problems of predicting the growth regimes of quasi-one-dimensional electronic structures - quantum nanowires based on three-component compounds A3B5. It is shown that modeling of growth processes of threads based on the Monte Carlo method can be an effective solution. The formation of quantum nanowires is carried out due to the external flow of particles transferred in the first series of experiments perpendicular to the substrate, in the second series - at random angles. The constructed model allows us to evaluate the effect of the composition on the geometric parameters of the formed objects. The critical thickness of quasi-one-dimensional structures is calculated. Conclusions are drawn about the control factors of the processes of thread growth. It is shown that compositional variations are an effective parameter for controlling the processes of formation of three-component 1D structures.
Keywords: quantum nanowires, Monte Carlo method, growth on a substrate, adsorption, diffusion, one-dimensional structures
The theoretical aspects of crystallization of multicomponent solid solutions are discussed. Antimonoid heterosystems in which bismuth is present are considered, a component that largely determines the photoelectric properties of the studied materials. The features of establishing the equilibrium of the liquid and solid phases in the process of crystallization of these systems are considered. The laws of the thermodynamic behavior of heterosystems in the conditions of gradient liquid-phase epitaxy are established. The results of experimental studies on the growth of solid solutions of multicomponent bismuthides on InSb substrates are presented.
Keywords: solid solutions, migrating liquid phase, indium antimonide arsenide, gallium bismuthide, binary pair, recrystallization, quasicrystalline structure
In this work, we simulated the graphene-MnO composite structure based on minimizing the electron density functional. The analysis of the processes of rearrangement of the interface surface SLG (monolayer of graphene) - MnО (111). In this case, the interface was subjected to hydrogenation. The distribution of the effective charge on graphene is investigated. A decrease in the work function of the charge carriers during hydrogenation of the interface is established.
Keywords: effective charge, graphene, passivated surface, density functional, interface, work function, energy gap, band structure
First-principles simulation of ultrathin amorphous carbon films has been performed. Nanohybrid graphene-C60 systems were considered. Total energy calculations were performed using pseudopotential method within density functional theory. Local atomic structure and electronic energy spectrum of the systems were studied. It was demonstrated that fullerene-graphene interaction results in significant deformation of their local atomic structure. Obtained results are in good agreement with experimental X-ray UV spectra of hydrogenated amorphous carbon
Keywords: Phase-change resistive memory, ab-initio simulation, pseudopotential method, Kohn-Sham method, graphene, fullerenes, amorphous carbon, atomic structure, electronic structure, adsorption energy
This paper contains an analysis of the modeling results of the electrophysical parameters of light-emitting GaInAsSb / GaSb solid solutions. The model takes into account three types of current - drift, thermionic emission and tunneling through potential barriers. In the work, graphs of radiation power versus current strength and current-voltage characteristic (IVC) of the LED device are plotted. Modeling indicators based on the features of the band structure of semiconductor systems have been built. Experimental results were discussed, which showed satisfactory agreement with the data obtained on the basis of calculations.
Keywords: solid solutions, Sim Windows 1,5, radiating structures, currents limited by space charge, electrophysical parameters
Developed approaches to measure the structural organization of systems. The concept of entropy expands and acts as an asymmetric criterion for the systems complexity. The necessity of a nonequilibrium approach to describing the interaction of physical structures and the possibility of interpreting entropy as a measure of the structural diversity of systems is shown. The validity of this approach is confirmed by a number of examples of the evolution of different systems, the structural distributions of the elements of which play an important role in modeling physical and physicochemical processes. Theoretical aspects are based on the fundamental work of D. Gibbs and L. Boltzman. The information content of the entropy concept correlates with the well-known “complementary” factor - coentropy. In this work, the evolution curves of complex systems are constructed as dependencies on statistical diversity. The symmetry of the functions of the density of entropy and coentropy with respect to the bifurcation points is discussed. It is shown that two-phase systems “liquid – vapor”, “crystal – melt” are characterized by inversion of evolutionary trajectories.
Keywords: entropy, negentropy, koentropy, orderliness measure, structural variety, normal distribution, dissipative systems, asymmetric structure, orthogonal distributions, dependence inversion
The paper contains an analysis of the results of experiments on obtaining radiative structures based on gallium antimonide, formed by the method of thermal melt migration in a semiconductor matrix. The epitaxial process modes within the selected range were optimized for such parameters as the wavelength corresponding to the fundamental transition, a small lattice discrepancy, a small discrepancy in the coefficients of thermal expansion of the growing TP and the matrix. An original effect is described - an increase in the solubility of the Bi content in solid solutions, isoperiodic binary compounds A3B5 under conditions of a gradient temperature field. This effect allows a wide variation in the optical parameters of the element base of instruments based on solid solutions of GaSbBi / GaSb. The mechanisms of the generation of dislocations in a crystallized solid solution and the features of electrophysical and photoelectric parameters are analyzed. A structural solution of a light-emitting diode with strip geometry is proposed.
Keywords: solid solutions, recrystallization, gradient liquid-phase epitaxy, thermomigration, indium antimonide-bismuthide, melt thickness, temperature gradient, components, growth coordinate, epitaxial layers
In this paper, the modeling of phase equilibria in multicomponent systems of A3B5 compounds was carried out and the compositions of the liquid phase equilibrated with a given solid solution were calculated. A model of excess thermodynamic functions is used, which takes into account the formation of associates in the melt near the solidus temperatures. The developed algorithm allows solving a direct problem (in which the input parameters are the growth temperature of the layers and the composition of the solid phase corresponding to the expected instrument characteristics) and the inverse problem (the growth temperature and composition of the solid solution are sought for the given liquid phase). The limiting concentrations of the alloying components, arsenic and bismuth, are determined. The structural and electrophysical characteristics of multicomponent semiconductor A3B5 heterosystems are discussed, the solid solutions of which crystallize from the liquid phase in a gradient thermal field. The mechanism for introducing impurities into the lattice of epitaxial layers of multicomponent solid solutions is described for the first time. With an increase in the thickness of the crystallizable film, the thermodynamically equilibrium substitution by antimony bismuth atoms is completed and the introduction of Bi atoms into the interstices takes place. The interaction of neighboring atoms with the valence electron shells of Bi becomes more symmetrical, which causes an increase in concentration. The concentration of film defects near its rear surface also increases. The obtained values of electrophysical parameters make it possible to draw a conclusion about the instrumental suitability of the materials under study.
Keywords: solid solutions, mesostructure, antimonide, alloying, liquid phase, phase transformations, binary compounds, associates, lattice constant, multicomponent systems
The paper contains an analysis of the results of experiments on obtaining radiative structures based on gallium antimonide, formed by the method of thermal melt migration in a semiconductor matrix. The epitaxial process modes within the selected range were optimized for such parameters as the wavelength corresponding to the fundamental transition, a small lattice discrepancy, a small discrepancy in the coefficients of thermal expansion of the growing TP and the matrix. An original effect is described - an increase in the solubility of the Bi content in solid solutions, isoperiodic binary compounds A3B5 under conditions of a gradient temperature field. This effect allows a wide variation in the optical parameters of the element base of instruments based on solid solutions of GaSbBi / GaSb. The mechanisms of the generation of dislocations in a crystallized solid solution and the features of electrophysical and photoelectric parameters are analyzed. A structural solution of a light-emitting diode with strip geometry is proposed.
Keywords: thermomigration, solid solutions, gradient epitaxy, diode with fine mes, gallium antimonide, fundamental transition, photoluminescence spectra
Band structure calculations were performed for quasi-2D MeO systems using the pseudopotential method within density functional theory. The calculations were carried out within the plane waves methodology using pseudopotentials. Density of electron states was calculated within the approxination of collinear magnetism. We examined the electron structure and estimated the electronic and magnetic properties of FM-ordered quasi-2D MeO systems (Me = Mn, Fe, Co, Ni). It has been demonstrated that the MnO - FeO - CoO - NiO row exhibits a shift in 3d spin down states of the metal relatively to the Fermi level towards the low-energy region. The above affects magnetization in 2D systems of oxides of 3d transition metals. The character of electron density distribution in quasi-2D MeO systems (Me = Mn, Fe, Co, Ni) indicates ionic bond type between the atoms in Me systems. The tendency towards increase of the band gap in the FeO→ CoO→ NiO row has been established. The obtained estimates of the local magnetic moment of a 3d transition metal atom in crystals of examined oxides correlate with experimental data. In conformity with existing views in physics, we have revealed the effect of spontaneous spin polarization of Me 3d and 2p bands of oxygen atoms in quasi-2D MeO systems (Me = Mn, Fe, Co, Ni), which in our opinion plays the main role in generation of magnetic moments in the atoms of 3d transition metal and oxygen.
Keywords: Density functional theory, pseudopotential mathod, ferromagnetism, electronic band structure, transition metal oxides