Equal Concentrations Of Electrons Research Articles

Особливості розпаду щільної плазми високовольтних імпульсних розрядів у воді, ініційованих електричним вибухом залізного провідника

The article presents the results of investigations of the decay coefficients of dense plasma in impulse discharges in water initiated by an electric explosion of an iron conductor. An analysis of time-resolved and spatial emission spectra of the discharges was performed, along with the study of absorption spectra dynamics with a 5 μs interval. The electron concentration of the dense plasma was determined at different time points, allowing the determination of its decay coefficients at electron concentrations ranging from 1020 to 1021 cm-3. It was found that under equal electron concentrations in the plasma, the decay coefficients of plasma with iron impurities are consistent with the decay coefficients of plasma with tungsten impurities.

Tunable quantum Hall edge conduction in bilayer graphene through spin-orbit interaction

Bilayer graphene, in the presence of a one-sided spin-orbit interaction (SOI) induced by a suitably chosen substrate, is predicted to exhibit unconventional quantum Hall states. The new states arise due to strong SOI-induced splittings of the eight zeroth Landau levels, which are strongly layer polarized, residing fully or partially on one of the two graphene layers. In particular, an Ising SOI on the meV scale is sufficient to invert the Landau level order between the $n=0$ and $n=1$ orbital levels under moderately weak magnetic fields $B\ensuremath{\lesssim}10$ T. Furthermore, when the Ising field opposes the $B$ field, the order of the spin-polarized levels can also be inverted. We show that, under these conditions, three different compensated electron-hole phases, with equal concentrations of electrons and holes, can occur at $\ensuremath{\nu}=0$ filling. The three phases have distinct edge conductivity values. One of the phases is especially interesting, since its edge conduction can be turned on and off by switching the sign of the interlayer bias.

Magnetoresistance in two-component systems.

Two-component systems with equal concentrations of electrons and holes exhibit nonsaturating, linear magnetoresistance in classically strong magnetic fields. The effect is predicted to occur in finite-size samples at charge neutrality due to recombination. The phenomenon originates in the excess quasiparticle density developing near the edges of the sample due to the compensated Hall effect. The size of the boundary region is of the order of the electron-hole recombination length that is inversely proportional to the magnetic field. In narrow samples and at strong enough magnetic fields, the boundary region dominates over the bulk leading to linear magnetoresistance. Our results are relevant for two-and three-dimensional semimetals and narrow band semiconductors including most of the topological insulators.

Laser annealing of radiation defects in low disordered layers

Abstract Carrier concentration and mobility dependences on the annealing temperature have been compared for the cases of thermal (10 min) and laser (8 ms) annealing of silicon, implanted with low doses of P+ ions. It was found that the recovery of concentration and mobility depended on the heating time in different ways. The laser annealing requires higher temperatures for mobility recovery then the thermal treatment. The same temperature shift was observed for increase of carrier concentration but only after doses less than 3.1012m−2. When the doses exceeded 3.1012 cm−2 laser and thermal annealing resulted in equal electron concentrations providing the equality of heating temperatures. Annealing of disordered regions was accounted for the mobility recovery. The increase of electron concentration was explained as an instantaneous decay of defect-impurity complexes. To check the validity of the assumptions laser annealing of electron and light ions irradiated materials was investigated.

On structural instabilities in itinerant magnets and superconductors

The influence of a structural distortion on the itinerant antiferromagnetic (IAF) phase and on the superconducting (S) phase is investigated using a free electron band structure for the electron and hole pockets. For equal concentrations of electrons and holes a metastable phase is found in which the lattice distortion coexists with the IAF or S phase. For unequal concentrations of electrons and holes the critical temperature and the value of the order parameter for the IAF or S phase (in the coexistence region) will always be enhanced by the onset of the structural distortion. The theoretical predictions are compared in the IAF case with the occurrence of a spin flip transition in chromium accompanied by a tetragonal distortion, and in the S case with experimental results on A-15 compounds exhibiting a martensitic phase transition.

Electronic processes at grain boundaries in polycrystalline semiconductors under optical illumination

The dependence of minority carrier lifetime (τ) on the doping concentration N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> , grain size <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</tex> and interface state density N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">is</inf> at the grain boundaries in (n-type) polycrystalline semiconductors has been calculated analytically. The recombination velocity at grain boundaries is enhanced by the diffusion potential V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> adjacent to the boundaries, and ranges from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\simeq 10^{2}</tex> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cm . s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> depending on N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">is</inf> and N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> . Under illumination, the population of the interface states is altered considerably from its dark level and as a result, V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> decreases to that value which maximizes recombination (equal concentrations of electrons and holes at the boundary). This causes τ to decrease with increasing N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> . Sample calculations for polycrystalline silicon show that for low angle boundaries with interface state densities of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\simeq 10^{11}</tex> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , τ decreases from 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> s as the grain size is reduced from 1000 to 0.1 µm (for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_{d} = 10^{16}</tex> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ). For a constant grain size, τ decreases with increasing N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> . The open-circuit voltage of p-n junction solar cells decreases for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\tau \leq 10^{-7}</tex> s, whereas that for Schottky barrier cells remains at its maximum value until <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\tau \lsim 10^{-8}</tex> s.

Metastable phase relationships in zinc-rich copper and silver alloys produced by rapid freezing

By using the very rapid freezing technique of “splat” cooling the two phase field between the cph η-terminal solid solution and the cph ε-phase have been explored in the Zn-Cu and Zn-Ag systems. Metastable extensions of both the η- and the ε-phases can be produced for all compositions in the two phase region. Nevertheless a discontinuity in structure remains between the metastable extensions of the stable phases at nearly equal electron concentrations: 1.912 for Zn-Ag and 1.9516 for Zn-Cu. The discontinuity, most clearly shown by the change in slope of unit cell volume with composition, occurs at nearly equal values of axial ratio: about 1.61. The result of the very rapid freezing has been to eliminate the equilibrium two phase field and to bring metastable ε and η phase fields together until they just touch one another. A consideration of thermodynamic arguments is presented to support the idea that the miscibility gap occurs not because of a hump in an otherwise continuous free energy curve for the solid phase but because the ε- and η-phases do correspond to two distinguishably different structures.

Quantum theory of thermogalvanomagnetic phenomena (TGMP) in conductors with equal concentration of electrons and holes

AbstractFor the case of a magnetic quantization field a method is developed to calculate the conductivity current and heat flow up to terms of 1/(Ωτ) 2; Ω and τ being the cyclotron resonance frequency of the carriers and the relaxation time, respectively. The kinetical coefficients, determined by these currents, are necessary for the investigation of TGMP in conductors with equal concentrations of electrons and holes and also of the oscillations of the Hall constant in normal conductors. For the scattering on a short‐range potential the dependence of σ(2)xy on the magnetic field is analysed.

Spiral waves and magnetoplasma resonance in metals with equal concentrations of electrons and holes

It is shown that in metals with equal electron and hole concentrations there can exist electromagnetic waves different from the Alfv̀en type. The spectrum of one of them has a limiting frequency that results in a new magnetoplasma resonance.