Anisotropic momentum transfer in low-dimensional electron systems in a magnetic field

In low-dimensional systems with an asymmetric quantizing potential, an asymmetric electron energy spectrum ε(p)≠ε(−p), where p is the electron momentum, arises in the presence of a magnetic field. A consequence of such an energy spectrum is that momentum transfer to the electron system in mutually opposite directions in the presence of an external perturbation is different. Therefore, in the presence of a standing electromagnetic wave momentum is transferred from the wave to the electrons, which gives rise to a new type of electromotive force. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 551–555 (25 October 1997)     

Trapped and free electrons in the near-anode region of a striated discharge

Spatial potential profiles and electron energy distribution functions are measured in the near-anode region of a striated neon glow discharge. It is discovered that potential wells of small depth adjacent to the anode appear on the spatial potential profiles at certain moments in time. The distribution functions measured in the potential wells have a pronounced maximum of slow electrons, which sharply distinguishes them from the distribution functions in the striation phases where there are no wells. The mechanism which shapes the electron distribution function for electrons trapped in a potential well is analyzed. A perturbing effect of the anode on the electron distribution function as the anode is approached is discovered experimentally, and an interpretation of this effect is given. Zh. Tekh. Fiz. 68, 25–32 (March 1998)     

Is the Pauli exclusion principle the origin of electron localisation?

ABSTRACT

In this work, we inquire into the origins of the electron localisation as obtained from the information content of the same-spin pair density, γ^{σ, σ}(r₂∣r₁). To this end, we consider systems of non-interacting and interacting identical Fermions contained in two simple 1D potential models: (1) an infinite potential well and (2) the Kronig–Penney periodic potential. The interparticle interaction is considered through the Hartree–Fock approximation as well as the configuration interaction expansion. Morover, the electron localisation is described through the Kullback–Leibler divergence between γ^{σ, σ}(r₂∣r₁) and its associated marginal probability. The results show that, as long as the adopted method properly includes the Pauli principle, the electronic localisation depends only modestly on the interparticle interaction. In view of the latter, one may conclude that the Pauli principle is the main responsible for the electron localisation.     

Dependence of the intrinsic line width of surface states on the wave vector: The Cu(111) and Ag(111) surfaces

The dependence of the intrinsic line width Γ of electron and hole states due to inelastic scattering on the wave vector k _∥ in the occupied surface state and the first image potential state on the Cu(111) and Ag(111) surfaces has been calculated using the GW approximation, which simulates the self-energy of the quasiparticles by the product of the Greens’s function and the dynamically screened Coulomb potential. Different contributions to the relaxation of electron and hole excitations have been analyzed. It has been demonstrated that, for both surfaces, the main channel of relaxation of holes in the occupied surface states is intraband scattering and that, for electrons in the image potential states, the interband transitions play a decisive role. A sharp decrease in the intrinsic line width of the hole state with an increase in k _∥ is caused by a decrease in the number of final states, whereas an increase in Γ of the image potential state is predominantly determined by an increase of its overlap with bulk states.     

Radiation annealing studies in ion bombarded MgO

Abstract

The energy distributions of convoy electrons produced at glancing angle incidence of fast ions are studied with Classical Trajectory Monte Carlo (CTMC) calculations. The image potentials both of the ion and of the convoy electron are taken into account. For light ions, the acceleration of the convoy electron by the ion's image potential is depressed by the image potential of the convoy electron, while for heavy ions this effect is negligible.     

DFT/TDDFT investigation on the photophysical properties of a series of phosphorescent cyclometalated complexes based on the benchmark complex FIrpic

The photophysical properties of four Ir(III) complexes have been investigated by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). The effect of the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption and phosphorescent properties has been studied. The theoretical calculation shows that the lowest-lying singlet absorptions for complexes 1–4 are located at 387, 385, 418 and 386 nm, respectively. For 1–4, the phosphorescence at 465, 485, 494 and 478 nm is mainly attributed to the LUMO → HOMO and LUMO → HOMO-1 transition configurations characteristics. In addition, ionisation potential (IP), electron affinities (EAs) and reorganisation energy have been investigated to evaluate the charge transfer and balance properties between hole and electron. The balance of the reorganisation energies for complex 3 is better than others. The difference between hole transport and electron transport for complex 3 is the smallest among these complexes, which is beneficial to achieve the hole and electron transfer balance in emitting layer.     

Electronic resonances in a quantum well having a periodically uneven boundary

The spectrum of the electronic states in an infinitely deep two-dimensional potential well, where one wall is periodically uneven, is investigated theoretically. It is shown that in non-Bragg type resonances — standing electron wave resonances, which are modes of different spatial harmonics of the electron wave function — arise in such a well. The resonances occur in a wide range of energies, starting at values close to the bottom in each 2D subband. The resonance interaction splits the energy spectrum and results in the appearance of gaps, giving the electron spectrum a miniband character. The properties of the electron gas vary substantially in accordance with the new characteristics of the spectrum. Fiz. Tverd. Tela (St. Petersburg) 41, 1867–1870 (October 1999)     

Electronic state confinement in a Hubbard chain

Electron redistribution over a 1D sublattice resulting from Hubbard repulsion leads to an effective two-particle interaction with a potential linear in coordinate difference. Two-particle wave functions and a narrow-band electron spectrum have been found. Fiz. Tverd. Tela (St. Petersburg) 40, 761–763 (April 1998)     

Transition radiation of a charge in media with a nonuniform potential

The influence of a potential barrier on the transition radiation in the form of volume and surface electromagnetic waves emitted by a charged particle crossing an interface between media is investigated. It is shown that the volume-wave radiation field arises not only as a result of the jump in the dielectric constant at the boundary but also as a result of the velocity jump and the reflection of an electron induced by the presence of a nonuniform potential barrier. The angular distribution of the transition radiation intensity is obtained. Zh. Tekh. Fiz. 68, 11–14 (January 1998)     

Theoretical design of azaacene-based non-fullerene electron transport material used in inverted perovskite solar cells

ABSTRACT

Inverted perovskite solar cells (PSCs) have attracted much attention due to their low-temperature and solution-based process. Electron transport layers are important components in inverted PSCs. Non-fullerene n-type organic small molecules seem to be more attractive as electron transport layers, because their structures are easy to be synthesised and modified. In this paper, density functional theory and semi-classical Marcus electron transfer theory were used to explore the electron transport properties in three azaacene derivatives, including one experimentally reported molecule, 1,4,9,16-tetrakis((triisopropylsilyl)ethynyl)quinoxalino[2^?,3^?:4^″,5^″]cyclopenta[1^″,2^″,3^″:5^′,6^′]acenaphtho[1^′,2^′:5,6]pyrazino[2,3-b]phenazine (1), and two theoretically designed molecules (2 and 3). Compound 2 is formed by substituting i-Pr groups in compound 1 with H atoms, which is designed to evaluate the effect of i-Pr groups on the electron transport properties. Compound 3 is designed by adding one more benzopyrazine group to the conjugation structure of compound 1. It shows that i-Pr group can increase HOMO and LUMO energy levels and improve solubility in organic solvent and hydrophobicity. Enlarging conjugation can not only decrease LUMO energy level and electron reorganisation energy, but also can increase solubility and electron mobility. So our designed compound 3 is expected to be a potential electron transport material in inverted PSCs.     

Quantum effects in rutherford back-scattering and emission of electrons near a crystal axis

Abstract

By increasing the strength of the interaction potential for a reasonable range of values, we show that the angular pattern of the electron intensity, about a crystallographic axis, changes from one dominated by Bragg peaks to an essentially structureless curve. This retains a significant dependence on h, and by that token cannot be identified with the ‘classical envelope’.     

Characteristic electron thermalization time in dielectric media

An approximate solution is obtained for the thermalization transport equation for electrons with an energy below the atom ionization potential. The results are used to estimate the thermalization time and the time of removal of the ionization electron from its atom in the gaseous and liquid states of inert gases. Zh. Tekh. Fiz. 67, 41–45 (June 1997)     

Features of the excitonic optical reflection curves of GaAs crystals

The excitonic optical reflection curves are investigated for GaAs crystals subjected to a surface-sensitive electron bombardment. The observed features of the curves can be explained on a qualitative level by using an extremely simple square-well approximation of the subsurface excitonic potential. Fiz. Tverd. Tela (St. Petersburg) 39, 610–612 (April 1997)     

Experimental investigation of nonlocality effects in the electron energy spectrum in an electronegative gas

The nonlocality of the electron energy distribution function (EEDF) in a dc discharge in oxygen is observed experimentally. A method is developed for measuring the isotropic part of the EEDF in a low-temperature plasma of electronegative gases. The radial dependence of the EEDF and the radial distributions of the electron density, the average electron energy, and the potential are determined. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 511–516 (10 April 1996)     

On the calculation of the tunnelling probability in a heavily-doped p-n junction

Abstract

The one-dimensional Schrodinger's equation for a triangular potential barrier (appropriate to tunnel diodes) is solved directly to obtain an expression for the probability of tunnelling of an electron through it. The result has been compared with that of Kane and the W.K.B. method. It is concluded that the results based on this calculation predict the same functional dependence of the tunnelling probability on m?, E_g and F as that predicted by earlier methods.     

Statistical theory of a solvated electron in an electrolyte

The behavior of a solvated electron in an electrolyte is investigated. The formalism of the theory is based on variational estimation of path integrals. It reduces the problem to the investigation of the self-consistent mean field produced by the ions and the electron. Mayer cluster expansions make it possible to take account of the short-range interactions and to find expressions for the effective potential of the electron and the electron-ion and electron-neutral atom correlation functions as a function of the macro-and microscopic parameters of electrolytes. In the limit of high ion densities the behavior of the electron is determined solely by the Coulomb interaction, which results in the formation of a polaron state. This state of the electron is virtually independent of the thermodynamic parameters of the electrolyte. In the opposite limit of low ion densities the electron forms a cavity state. The presence of ions results in additional localization of the electron and is manifested experimentally as a shift of the absorption band in the direction of high energies. The estimated shift for a hydrated electron agrees with the experimental data. Zh. éksp. Teor. Fiz. 115, 1463–1477 (April 1999)     

Derivation of the vacuum longitudinal fieldB (3) from the Dirac equation of the electron in the electromagnetic field

By solving the Diras equation for the motion of an electron (c) in the circularly polarized electromagnetic field it is shown that the intrinsic electron spin forms an interaction Hamiltonian with a time independent fieldB ⁽³⁾ of electromagnetic radiation in the vacuum. In the same way as intrinsic spin is a fundamental property of the electron,B ⁽³⁾ is therefore a fundamental and intrinsic property of the vacuum electromagnetic field.     

Spectroscopy of electroreflection, the electron band structure, and the mechanism of visible photoluminescence of anisotropically etched silicon

We present the results of studies of electroreflection in the 1.1–4.4 eV spectral range, of electron Auger spectroscopy, and of electron diffraction involving the photoluminescent Si-SiO₂ system prepared via anisotropic chemical etching of the Si(100) surface. These results are explained on the basis of a four-layer model of the band structure and energy transition diagram for a system with a quantum well at the silicon surface, surface electron states at the boundary, and a gradient of the band potential in the transition layer. We find that light-emitting silicon remains an indirect-gap semiconductor and that the visible photoluminescence is due to direct recombinations of the light-excited electrons and holes in the quantum well at the center of the Brillouin zone with the participation of the band of deep localized states, which is due to the presence of oxygen at the silicon surface. Zh. éksp. Teor. Fiz. 116, 1750–1761 (November 1999)     

Lattice Dynamics of Some Fcc F-Shell Metals

A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the binding energy, equation of state, ion-ion interaction, phonon dispersion curves (q-space and r-space analysis), phonon density of states, Debye temperature, mode Grüneisen parameters, dynamical elastic constants, Debye-Waller factor, mean-square displacement, Debye-Waller temperature parameter and propagation velocities of elastic waves of some fcc f-shell metals La, Yb, Ce, and Th. The contribution of the s-like electrons is calculated in the second-order perturbation theory for the model potential while d- and f-like electron is taken into account by introduction of repulsive short-range Born-Mayer term. Very recently proposed screening function due to Sarkar et al. has been used to obtain the screened form factor. The parameter of the potential is evaluated by zero pressure condition. Which is independent of any fitting procedure. An excellent agreement between theoretical investigations and experimental findings prove the ability of the potential for d- and f-shell metals exclusively.     

System of quantum wells in a parallel magnetic field

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)