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1.
The energy spectrum and quantum states of electrons in a system of quantum wells in a strong magnetic field parallel to the
heterogeneous boundaries are studied. The combined effect of the quantizing magnetic field and the potential of the system
of quantum wells leads to a radical change in the electron dispersion relation owing to the appearance of one-dimensional
Landau bands. The neighborhoods of the anticrossing points of the different bands correspond to an effective redistribution
of the electron envelope functions, which becomes stronger as the magnetic field is raised. The character of the electron-state
density in the size-quantization subbands is examined qualitatively in connection with the change in the system of isoenergy
contours when a magnetic field is applied.
Fiz. Tverd. Tela (St. Petersburg) 40, 1719–1723 (September 1998) 相似文献
2.
Shon C.H. Lee J.K. Lee H.J. Yang Y. Chung T.H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(6):1635-1644
Results of the particle simulation of magnetron sputter are presented. Using a kinetic code, we obtain the spatial profiles of plasma density, potential, and velocity distribution function, along with the electron temperature, the ion density, the current density, and the deposition profiles at the anode surface. The result of simulation is compared with the Child-Langmuir law applied to the magnetron discharge and the global model. The velocity distribution function of electrons is Maxwellian, but that of ions is non-Maxwellian near the cathode with the majority in the energy range below 50 eV 相似文献
3.
The plasma region under investigation is separated from the discharge region by a mesh grid. Plasma potential and electron number densities and electron temperatures under bi‐Maxwellian approximation for electron distribution function of the multi‐dipole argon plasma are measured. The cold electrons in the diffusion region are produced by local ionization. The hot electrons are the ionizing electrons behaving as Maxwellian. The electron trapping process in the discharge region is produced by potential well due to positive plasma potential with respect to the anode and by a repulsive grid. The dependence of ratios of the density of the hot to the cold electrons NE (=Neh/Nec) and hot to cold electron temperature T(=Teh/Tec) in the diffusion region on the depth of the potential well has been investigated. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
N. I. Alekseev 《Technical Physics》1998,43(5):535-538
The influence of the escape of fast plasma electrons on the electron distribution function (EDF) in a low-voltage cesium Knudsen
arc is discussed. It is shown that even with a large Knudsen parameter l
e
/h∼5–10 (where h is the gap and l
e
is the mean free path of electrons with energy of the order of the anode barrier) the electron flux from the plasma to the
anode is virtually identical to that calculated with a Maxwellian EDF.
Zh. Tekh. Fiz. 68, 61–64 (May 1998) 相似文献
5.
We report for the first time the Compton profiles of electron momentum distribution inβ-gallium calculated along the crystallographic directions (100), (110) and (111). The conduction electron states for this
purpose are determined in the energy band calculations using model potential. The core states, on the other hand, are represented
each by a single tight-binding function. The results show that the Compton profiles are nearly isotropic with very little
directional dependence, which is suggestive of a free-electron-like distribution of the conduction electrons in this system.
The latter conclusion is in close confirmity with similar conclusions drawn in augmented plane wave (APW) calculation of energy
bands and the derived Knight-shift results inβ-Ga. 相似文献
6.
Qiuji Zhao Ting Mei Daohua Zhang Oka Kurniawan 《Optical and Quantum Electronics》2011,42(11-13):705-711
We carry out a theoretical analysis of wetting layer effect on band-edge profiles and electronic structures of InAs/GaAs truncated-pyramid quantum dots, including the strain effect. A combination of an analytical strain model and an eight-band Fourier transform-based k · p method is adopted in the calculation. Strain modified band-edge profiles indicates that wetting layer widens the potential well inside the dot region. Wetting layer changes ground-state energy significantly whereas modifies probability density function only a little. The main acting region of wetting layer is just underneath the base of the dot. Wetting layer redistributes probability density functions of the lowest electron state and probability density functions of highest hole state differently because of the different action of quantum confinement on electrons and holes. 相似文献
7.
Yu. B. Golubovskii V. O. Nekuchaev N. S. Ponomarev I. A. Porokhova 《Technical Physics》1997,42(9):997-1003
Numerous papers have been devoted to the investigation of striations in inert gases at low pressures (p⩽2 Torr) and small currents (i<100 mA) [A. V. Nedospasov, Sov. Phys. Usp. 11, 174 (1968); L. Pekarek, Sov. Phys. Usp. 11, 188 (1968); N. L. Oleson and A. W. Cooper, Adv. Electron. Electron Phys. 24, 155 (1968); P. S. Landa, N. A. Miskinova, and Yu. V. Ponomarev, Sov. Phys. Usp. 23, 813 (1980)]. Since the nature of striations is determined under these conditions by the nonlocal kinetics of the electrons
in spatially periodic fields [L. D. Tsendin, Sov. J. Plasma Phys. 8, 228 (1982)], an investigation of the electron distribution function in space and time would be very interesting. The purpose
of the present work is to experimentally investigate the potential profiles and distribution functions in S and P striations and to analyze the mechanism which shapes the distribution functions for striations of these types.
Zh. Tekh. Fiz. 67, 14–21 (September 1997) 相似文献
8.
L. I. Korovin I. G. Lang S. T. Pavlov 《Journal of Experimental and Theoretical Physics》1997,84(6):1197-1208
The spatial correlation of light-generated electrons and holes in a quasi-two-dimensional electron gas in a strong magnetic
field is investigated in an approximation linear in the intensity of the exciting light. The correlation is due to the interaction
of the electrons and holes with longitudinal optical (LO) phonons. The theory permits calculating, on the basis of a special diagrammatic technique, two distribution functions of
an electron-hole pair with respect to the distance between the electron and the hole after the emission of N phonons: first, the function determining the total number of pairs which have emitted N phonons and, second, the function related to the rank-4 light-scattering tensor in interband resonance Raman scattering of
light. A special feature of the system is that the electron and hole energy levels are discrete. The calculation is performed
for a square quantum well with infinitely high barriers. The distribution function and the total number of electron-hole pairs
before the emission of phonons as well as the distribution function corresponding to two-phonon resonance Raman scattering
are calculated. The theory predicts the appearance of several close-lying peaks in the excitation spectrum under resonance
conditions. The number of peaks is related to the number of the Landau level participating in the optical transition. The
distance between peaks is determined by the electron-phonon coupling constant. Far from resonance there is one peak, which
is much weaker than the peaks obtained under resonance conditions.
Zh. éksp. Teor. Fiz. 111, 2194–2214 (June 1997) 相似文献
9.
The form of the electron distribution function in the positive column of low-pressure discharges is examined under conditions
such that the electron mean free path exceeds the vessel radius. Its formation is analyzed taking all major factors into account,
including elastic and inelastic collisions, radial and axial electric fields, and the loss of fast electrons to the wall.
It is shown that the main mechanism controlling the fast part of the distribution function is the loss of electrons to the
wall, which is determined by the scattering of electrons into a comparatively small loss cone that depends on the relationship
between the axial and radial components of the velocity. Since the elastic collision rate for all elements has a weak dependence
on the energy beyond the ionization threshold, ultimately the high-energy part of the electron energy distribution function
in the positive column of low-pressure discharges is nearly Maxwellian. The subthreshold portion of the distribution function,
in turn, is determined by the energy diffusion, in a comparatively strong field, of Maxwellian electrons which arrive after
inelastic collisions. The final electron distribution function is well approximated by an exponential with a single slope
over the entire energy range. Only within a narrow range of scattering angles is the electron distribution function strongly
depleted by the loss of electrons to the vessel walls. In the end, it is concluded that this phenomenon, like the Langmuir
paradox, may be related to aspects of the physics of the formation of the electron distribution function owing to a combination
of already known mechanisms, rather than to a hypothetical mechanism for thermalization of the electrons, as assumed up to
now in the literature. A comparison of solutions of the model kinetic equation given here with published Monte Carlo calculations
and experimental data shows that they are in good agreement.
Zh. Tekh. Fiz. 69, 34–41 (November 1999) 相似文献
10.
We consider the anode plasma structure in a gas discharge with density of neutral atoms (neutrals) depleted by strong ionization. We obtain analytical solutions of the quasi-neutrality equation for the potential distribution and a condition for the existence of anode plasma in the one-dimensional case for arbitrary potential dependences of the neutral depletion frequency and the electron density. We consider the special cases of a constant neutral depletion frequency, ionization by Maxwellian electrons, and ionization by an intense electron beam under the conditions of collisionless ion motion and Boltzmann thermal electron distribution. The solutions for the first two cases at zero depletion parameter, i.e., at constant gas density, match those obtained in [1] by a power series expansion. In the case of ionization by Maxwellian electrons, the formation of anode plasma at reasonable working-gas flow rates is shown to be possible only at a fairly high electron temperature (if, e.g., xenon is used as the working gas, then T e ≥ 5 eV). Steady-state solutions of the quasi-neutrality equation under ionization by an intense electron beam exist only if the ratio of the electron beam density to the maximum thermal electron density does not exceed a certain limiting value. 相似文献
11.
V. F. Elesin A. V. Krasheninnikov 《Journal of Experimental and Theoretical Physics》1997,84(2):375-382
The paper presents a numerical solution of a system of nonlinear equations for the electron distribution functions in the
upper and lower subbands between which lasing transitions occur and the number of nonequilibrium optical phonons in semiconducting
cascade lasers based on quantum wells and wires. For the case of quantum wells, we propose an analytical solution of this
system of equations, which is a generalization of the previously found solution [V. F. Elesin and Yu. V. Kopaev, Zh. éksp.
Teor. Fiz. 108, 2186 (1995) [JETP 81, 1192 (1995)]; V. F. Elesin and Yu. V. Kopaev, Sol. St. Commun. 96, 897 (1995)] in a wider range of injection rates. The threshold injection rate can be significantly reduced owing to reabsorption
and accumulation of nonequilibrium optical phonons, nonparabolicity of the subbands and different effective masses of electrons
in different subbands. In the case of quantum wires, the threshold injection rate is considerably lower, and its decrease
is even larger than in quantum wells. It is remarkable that, owing to the lower electron-electron relaxation rate in the one-dimensional
case, the decrease in the threshold injection rate may be two or three orders of magnitude. The relation between the density
of states and threshold current has also been studied.
Zh. éksp. Teor. Fiz. 111, 681–695 (February 1997) 相似文献
12.
Room temperature Compton profiles of momentum distribution of conduction electrons in α -Ga metal are calculated in band model.
For this purpose, the conduction electron wave functions are determined in a temperature-dependent non-local model potential.
The profiles calculated along the crystallographic directions, (100), (010), and (001) are found to be nearly isotropic. This
conclusion is in reasonable agreement with experimental observations 相似文献
13.
V. V. Valyaev V. L. Gurtovoi D. Yu. Ivanov S. V. Morozov V. V. Sirotkin Yu. V. Dubrovskii S. Yu. Shapoval Yu. N. Khanin E. E. Vdovin A. N. Pustovit 《Journal of Experimental and Theoretical Physics》1998,86(2):383-387
Electrophysical parameters of single and double delta-doped layers in GaAs epitaxial films grown by the metal-organic chemical
vapor deposition have been systematically investigated in the temperature range of 4.2 to 300 K. The 2D electron gas density
distribution is affected by the overlap of wave functions in neighboring quantum wells, as a result of which the peak on the
curve of the Hall mobility in the 2D electron gas versus the separation between the quantum wells shifts. The persistent photoconductivity
in delta-doped layers is due to the change in the surface potential caused by the neutralization of the negative charge of
surface states by photoexcited holes. A method for comparing delta-doped layers grown under different conditions at different
depths from the sample surface has been suggested.
Zh. éksp. Teor. Fiz. 113, 693–702 (February 1998) 相似文献
14.
V. V. Ivanov T. V. Rakhimova A. O. Serov N. V. Suetin A. F. Pal’ 《Journal of Experimental and Theoretical Physics》1999,88(6):1105-1114
Elementary processes in dusty, beam-driven plasma discharges are studied experimentally and theoretically for the first time.
A theoretical model is constructed for a beam-driven plasma containing macroscopic particles. The effect of macroscopic particles
on the electron energy distribution function is estimated assuming a Coulomb field for the particles. The resulting rate of
electron-ion recombination on the macroscopic particles is compared with the electron loss constant calculated from the electron
energy distribution function with an electron absorption constant in the orbital-motion approximation. This approximation,
which is valid in the collisionless case, is found to work satisfactorily beyond its range of applicability. The distributions
of the charged particles and electric fields created by macroscopic particles in a helium plasma are determined. The experimental
data demonstrate the importance of secondary emission by high-energy electrons.
Zh. éksp. Teor. Fiz. 115, 2020–2036 (June 1999) 相似文献
15.
为了研究靶材料对快电子能量分布的影响,采用电子谱仪测量了飞秒激光与Cu和CH靶相互作用中在靶前和靶后产生的快电子能谱。结果显示,在靶前Cu和CH靶的快电子能谱相似,反应了快电子发射对靶材料的依赖性较弱;在靶后Cu和CH靶的快电子能谱具有明显的差异,说明电子的输运过程与靶材料密切相关。冷电子环流以及自生磁场是导致Cu靶快电子能谱"软化"的原因,而对于CH靶麦克斯韦分布的快电子能谱主要由碰撞机制决定。 相似文献
16.
The distribution function of bound electrons and the recombination rate of electrons and ions in the presence of two-level
atoms is considered within a diffusion model. Two cases are considered: (a) it is assumed in accordance with traditional theories
that relaxation occurs as a result of binary collisions; (b) it is assumed that the anomalous drift previously discovered
on the basis of a first-principles simulation takes place. It is shown that the distribution of bound electrons obtained on
the basis of the theory of binary Coulomb collisions is not consistent with the results of a numerical many-particle dynamics
simulation, while a kinetic model which utilizes the theory of anomalous drift is consistent with the simulation results.
Zh. Tekh. Fiz. 68, 15–19 (January 1998) 相似文献
17.
We present a new method to obtain high-mobility three-dimensional electron gas systems. We have achieved control of carrier density and of carrier profile by growth of the first remotely-doped parabolic potential well structures. Computer-controlled molecular beam epitaxy is used to grow a layer of ultra-fine superlattices with a programmable composition gradient. This produces conduction-band potentials which, in the absence of doping, are equivalent to the potential profiles of fixed charge distributions. When conduction electrons are introduced into these graded wells through remote doping of the barrier regions, they distribute themselves in such a way as to produce a uniform chemical potential at thermal equilibrium. We illustrate through computer simulations employing Fermi statistics that electrons introduced into a wide parabolic potential well distribute themselves uniformly. More significantly, the carrier distribution in the well is remarkably insensitive to the dopant sheet charge in the barrier, the more so at lower temperatures. We have fabricated remotely-doped graded potential well structures of the proposed type by molecular beam epitaxy. These structures exhibit the above effects. Measured mobilities of such three-dimensional electron gases grown using the GaAs/AlxGa1−xAs system are higher than those of bulk-doped GaAs doped to give the same uniform electron concentration. 相似文献
18.
V. B. Timofeev A. V. Larionov P. S. Dorozhkin M. Bayer A. Forchel J. Straka 《JETP Letters》1997,65(11):877-882
When a voltage is applied to double quantum wells based on AlGaAs/GaAs heterostructures with contact regions (n-i-n structures), a two-dimensional (2D) electron gas appears in one of the quantum wells. Under illumination which generates
electron-hole pairs, the photoexcited holes become localized in a neighboring quantum well and recombine radiatively with
the 2D electrons (tunneling recombination through the barrier). The appearance, ground-state energy, and density of the degenerate
2D electron gas are determined from the structure of the Landau levels in the luminescence and luminescence excitation spectra
as well as from the oscillations of the radiative recombination intensity in a magnetic field with detection directly at the
Fermi level. The electron density is regulated by the voltage between the contact regions and increases with the slope of
the bands. For a fixed slope of the bands the 2D-electron density has an upper limit determined by the resonance tunneling
of electrons into a neighboring quantum well and subsequent direct recombination with photoexcited holes.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 11, 840–845 (10 June 1997) 相似文献
19.
The possibility of constructing a self-consistent model for the sustaining of ionization waves is demonstrated for a low-pressure
discharge in an inert gas. The model is based on the combined solution of the kinetic equation of the electrons and the equation
of motion of the ions in a spatially periodic field. The distribution function is constructed in an experimentally measured
field and then used to calculate the spatial distributions of the plasma density and the ionization rate. The solution of
the equation of motion of the ions makes it possible to reconstruct a field similar to the original one. One specific feature
of the mechanism considered is the pronounced nonlocal character of the formation of the electron distribution function by
the entire nonuniform potential profile of the ionization wave.
Zh. Tekh. Fiz. 67, 24–30 (February 1997) 相似文献
20.
由于缺乏详细的理论计算和实验结果,在研究绝缘壁面稳态流体鞘层特性时,通常假设壁面出射的总二次电子服从单能分布(0)、半Maxwellian分布等.在单能电子轰击壁面的详细二次电子发射模型基础上,采用Monte Carlo方法统计发现:当入射电子服从Maxwellian分布时,绝缘壁面发射的总二次电子服从三温Maxwellian分布.进而,采用一维稳态流体鞘层模型进行对比研究,结果表明:二次电子分布函数对鞘边离子能量、壁面电势、电势及电子/离子密度分布等均具有明显影响;总二次电子服从三温Maxwellian分布时,临界空间电荷饱和鞘层无解,表明随着壁面总二次电子发射系数的增加,鞘层直接从经典鞘层结构过渡到反鞘层结构. 相似文献