Alternation of nonequilibrium and sequences of structural transitions

An analysis is made of the law of alternating nonequilibrium, dictating an oscillatory change in the degree of nonequilibrium for a wide range of influence. With increasing influence, intervals of decreasing degree of nonequilibrium at their onset correspond to structural transitions and accompanying anomalous states. This law can be used to identify a wide variety of new nonequilibrium effects. Pis’ma Zh. Tekh. Fiz. 23, 17–21 (May 26, 1997)     

Kinetics of electron states of hydrogen molecules in nonequilibrium discharges: Singlet states

This study continues previous publications devoted to kinetic processes in nonequilibrium hydrogen plasma. This review contains an analysis of the kinetics of hydrogen molecules in the ground state and in excited singlet electron states in various gas discharges. The distribution functions measured over the vibrational levels of a hydrogen molecule in the ground electron state are compared with those calculated within the developed level semiempirical collisional-radiative model of low-temperature hydrogen plasma. A database of the measured and calculated collisional-radiative characteristics of kinetic processes involving excited hydrogen molecules and the parameters of low-temperature hydrogen plasma is formed.     

Relaxation of nonequilibrium states of a uniaxial ferromagnet

Relaxation of the nonequilibrium state of a uniaxial ferrimagnetic is studied. It is shown that the character of evolution of the magnetization vector is determined by anisotropy of the dissipation tensor.     

Observation of interface carrier states in no-common-atom heterostructures ZnSe/BeTe

The existence of intrinsic carrier interface states in heterostructures with no common atom at the interface (such as ZnSe/BeTe) is shown experimentally by ellipsometry and photoluminescence spectroscopy. These states are located on interfaces and lie inside the effective bandgap of the structure; they are characterized by a high density and a long lifetime. A tight binding model confirms theoretically the existence of these states in ZnSe/BeTe heterostructures for a ZnTe-type interface, in contrast to the case of the BeSe-type interface for which they do not exist.     

Photoelectric memory in epitaxial n-GaAs films

The resistivity of thin Bi films on silicon was measured for films of various thicknesses. The experimentally obtained thickness dependence of the resistivity was compared with the result of a numerical calculation based on the equation which was proposed by Mayadas and Shatzkes. At 290 K the experimental curve fitted the numerical one with surface and grain boundary reflection coefficients of 0.6 and 0.12 respectively.     

Hydrogen passivation studies in Pd/n-GaAs devices

The effect of hydrogen on the current (I-V) and capacitance (C-V, TSCAP) has been studied for Pd/n-GaAs diodes. Hydrogenation has been found to improve ideality factor of the diode. ReverseC-V characteristics show that the number of shallow and deep donors is reduced on hydrogenation. The TSCAP measurement shows the presence of two donor states at ∼ 0.48 and 0.72 eV which is being partially passivated on hydrogenation. The likely origin of these states is discussed.     

Effect of hydrogenation on defect levels in bulk n-GaAs

The hydrogenation effects on the defect levels existing in bulk n-GaAs were investigated by deep-level transient spectroscopy and photoluminescence. The three electron traps of the GaAs bulk samples were observed, and their activation energies wereE _c — 0.35 eV (E1), 0.56 eV (E2), and 0.81 eV (E3). After hydrogenation at 250 °C for 3 h, the electron trap atE _c — 0.35 eV was almost completely passivated and a new trap (EN1) atE _c — 0.43 eV was observed. As a result of furnace annealing for 5 min at 300 °C, the EN1 trap disappeared, and the E3 trap passivated by hydrogenation reappeared. In particular, the trap E1 recovered to 90%. The photoluminescence measurements of the hydrogenated samples show that the germanium-related peak was passivated, and the intensity of the dominant bound exciton peak increased remarkably. After a thermal annealing for 15 min at 300 °C, the original intensity of the germanium-related peak was restored.     

Vibrational nonequilibrium in gases

Conclusions The stationary and quasistationary distribution functions of the vibrational energy considered in this survey include all the basic types of vibrational distributions and have a sufficiently general nature. This generality is determined primarily by the fact that the stationary or quasistationary modes are, as a rule, compulsory of any nonequilibrium process. The clarification of the governing role of the quasistationary stage during a nonequilibrium process is the main result in the area of vibrational kinetics in recent years, which discloses extensive possibilities for controlling nonequilibrium processes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 935–949, November, 1977.     

Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots

We examine the population dynamics of multiple excitons in PbS quantum dots using spectrally resolved ultrafast supercontinuum transient absorption (SC-TA) measurements. We simultaneously probe the first three excitonic transitions. The transient spectra show the presence of bleaching of absorption for the 1S(h)-1S(e) transition, as well as transients associated with the 1P(h)-1P(e) transition. We examine signatures of carrier multiplication (multiple excitons arising from a single absorbed photon) from analysis of the bleaching features in the limit of low absorbed photon numbers (left angle bracket N(abs) right angle bracket ～ 10(-2)) for pump photon energies from two to four times that of the band gap. The efficiency of multiple-exciton generation is discussed both in terms of the ratio between early- to long-time transient absorption signals and of a broadband global fit to the data. Analysis of the population dynamics shows that bleaching associated with biexciton population is red shifted with respect to the single exciton feature, which is in accordance with a positive binding energy for the biexciton.     

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

Abstract

Adaptive wear-resistant coatings produced by physical vapor deposition (PVD) are a relatively new generation of coatings which are attracting attention in the development of nanostructured materials for extreme tribological applications. An excellent example of such extreme operating conditions is high performance machining of hard-to-cut materials. The adaptive characteristics of such coatings develop fully during interaction with the severe environment. Modern adaptive coatings could be regarded as hierarchical surface-engineered nanostructural materials. They exhibit dynamic hierarchy on two major structural scales: (a) nanoscale surface layers of protective tribofilms generated during friction and (b) an underlying nano/microscaled layer. The tribofilms are responsible for some critical nanoscale effects that strongly impact the wear resistance of adaptive coatings. A new direction in nanomaterial research is discussed: compositional and microstructural optimization of the dynamically regenerating nanoscaled tribofilms on the surface of the adaptive coatings during friction. In this review we demonstrate the correlation between the microstructure, physical, chemical and micromechanical properties of hard coatings in their dynamic interaction (adaptation) with environment and the involvement of complex natural processes associated with self-organization during friction. Major physical, chemical and mechanical characteristics of the adaptive coating, which play a significant role in its operating properties, such as enhanced mass transfer, and the ability of the layer to provide dissipation and accumulation of frictional energy during operation are presented as well. Strategies for adaptive nanostructural coating design that enhance beneficial natural processes are outlined. The coatings exhibit emergent behavior during operation when their improved features work as a whole. In this way, as higher-ordered systems, they achieve multifunctionality and high wear resistance under extreme tribological conditions.     

Oscillation in a nonequilibrium superconductor

Using the ^*-model and the Rothwarf-Taylor equations, this paper predicts that a superconductor will oscillate between two nonequilibrium superconducting states with different energy gaps when quasiparticles are injected at the edge of the energy gap through the tunneling effect. The main sources of origin of this oscillation are the quasiparticle injection at the gap edge and the existance of recombination phonons with energy = 2(n). Under certain nonequilibrium conditions, the recombination phonon system does not take part in Cooper pair-breaking processes and can further stimulate the quasiparticles to recombine into pairs. The uncertainty N_p of the number N _pof Cooper pairs has the same order of magnitude as N _pitself in such an oscillating superconductor, so that the phase of the wave function has a definite value. If superconducting weak coupling is formed between such two oscillating superconductors, this system should be described in the -representation.     

Brownian diffusion in nonequilibrium gas

The Brownian motion in a nonequilibrium gas is considered within the framework of the stochastic transfer theory in linear Boltzmann systems. The equation for Brownian diffusion of particles is derived in inhomogeneous flows of rarefied gas.     

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

Adaptive wear-resistant coatings produced by physical vapor deposition (PVD) are a relatively new generation of coatings which are attracting attention in the development of nanostructured materials for extreme tribological applications. An excellent example of such extreme operating conditions is high performance machining of hard-to-cut materials. The adaptive characteristics of such coatings develop fully during interaction with the severe environment. Modern adaptive coatings could be regarded as hierarchical surface-engineered nanostructural materials. They exhibit dynamic hierarchy on two major structural scales: (a) nanoscale surface layers of protective tribofilms generated during friction and (b) an underlying nano/microscaled layer. The tribofilms are responsible for some critical nanoscale effects that strongly impact the wear resistance of adaptive coatings. A new direction in nanomaterial research is discussed: compositional and microstructural optimization of the dynamically regenerating nanoscaled tribofilms on the surface of the adaptive coatings during friction. In this review we demonstrate the correlation between the microstructure, physical, chemical and micromechanical properties of hard coatings in their dynamic interaction (adaptation) with environment and the involvement of complex natural processes associated with self-organization during friction. Major physical, chemical and mechanical characteristics of the adaptive coating, which play a significant role in its operating properties, such as enhanced mass transfer, and the ability of the layer to provide dissipation and accumulation of frictional energy during operation are presented as well. Strategies for adaptive nanostructural coating design that enhance beneficial natural processes are outlined. The coatings exhibit emergent behavior during operation when their improved features work as a whole. In this way, as higher-ordered systems, they achieve multifunctionality and high wear resistance under extreme tribological conditions.     

Specific features of nonequilibrium depletion accompanied by the trapping of minority carriers by surface states in metal–insulator–semiconductor structures

Specific features (abrupt changes in current caused by voltage variation) of nonequilibrium depletion in metal–insulator–semiconductor structures based on gallium arsenide and silicon with a 40-nm-thick film of yttria-stabilized zirconia were revealed. These features may help extend the range of application of the nonequilibrium depletion effect in microelectronics.     

Comparative study of terahertz radiation from n-InAs and n-GaAs

We have studied terahertz (THz) emissions from n-InAs and n-GaAs using an ensemble Monte Carlo method. Our simulations indicate that higher amplitude THz waves from n-InAs, compared with those from n-GaAs, result from the difference in the radiation mechanisms between these two samples and are not completely dependent on the most commonly recognized fact: lighter electron effective mass in n-InAs. The excitation-wavelength-dependent and doping-level-dependent THz emissions from n-InAs are found to be quite different from those from n-GaAs. The corresponding mechanisms are analyzed by the introduction of a weighted electric field, which is weighted by the photogenerated carrier density in a semiconductor. The simulated results are in good qualitative agreement with experimental observations from other authors.     

拟交错逼近的参量误差估计

在实际计算离散最佳逼近时，通常仅得到“拟最佳”（即有ε－拟交错性质）逼近，故有必要估计（未知）最佳逼近与计算得到逼近之间的误差。文中借助于广义强单一性常数去估计逼近中的参量误差。     

Generators of nonequilibrium low-temperature plasma

Results are described of a study and of the characteristics of sources of a non-equilibrium gas-discharge plasma.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 966–975, December, 1987.     

Scanned electron beam irradiation of Ti Schottky contacts to n-GaAs

Ti Schottky contacts were formed on n-GaAs surfaces and irradiated using a low energy scanned electron beam at various fluence levels from 10¹⁵ to 10¹⁸ cm^–2. For fluence levels up to 10¹⁷ cm^–2, the Schottky contacts were found to exhibit a reduction in their leakage currents and increased barrier voltages. For fluence levels in excess of 10¹⁷ cm^–2, the Schottky diodes were found to exhibit significantly increased leakage currents and barrier voltages. The changes in leakage currents were consistent with the changes in their respective interface state density (D _it) values. However, the electron beam irradiation had little or no effect on the diode ideality factorn.     

A nonlinear critical layer in nonequilibrium gas

The method of matched asymptotic expansions is used to analyze the evolution of disturbances of a nonequilibrium compressible boundary layer on a flat plate in the region of nonlinear critical layer. A dispersion relation is obtained for low-amplitude subsonic disturbances. An equation is derived, which describes the evolution of disturbance in the nonlinear stage of its development. It is demonstrated that, similar to the case of equilibrium media, the increase in the disturbance amplitude in the given stage of development of turbulence exhibits an explosive pattern. The characteristic time of instability decreases with increasing degree of disequilibrium of the medium.