The atomic and electron structure of ZrO2

The atomic structure of amorphous and crystalline zirconium dioxide (ZrO₂) films is studied using X-ray diffraction and extended X-ray absorption fine structure techniques. The electron structure of ZrO₂ is experimentally determined using X-ray and UV photoelectron spectroscopy, and the electron energy band structure is theoretically calculated using electron density functional method. According to these data, the valence band of ZrO₂ consists of three subbands separated by an ionic gap. The upper subband is formed by the O2p states and Zr4d states; the medium subband is formed by the O2s states; and the narrow lower subband is formed predominantly by the Zr4p states. The bandgap width in amorphous ZrO₂, as determined using the electron energy loss spectroscopy data, amounts to 4.7 eV. The electron band structure calculations performed for a cubic ZrO₂ phase point to the existence of both light (0.3m ₀) and heavy (3.5m ₀) holes, where m ₀ is the free electron mass. The effective masses of band electrons in ZrO₂ fall within (0.6–2.0)m ₀.     

Spin edge states in two-dimensional electron systems

We consider the spin edge states, induced by the combined effect of spin-orbit interaction and hard-wall confining potential, in a two-dimensional electron system exposed to a perpendicular quantizing magnetic field. We derive an exact analytical formula for the dispersion relations of spin edge states and analyze their energy spectrum, velocity, and average transverse position. It is shown that by removing the spin degeneracy, spin-orbit interaction splits the spin edge states not only in the energy but also induces their spatial separation. It is revealed that at low magnetic fields, due to the Stark splitting of the spin-resolved edge states, the high-energy bands exhibit anti-crossings. This results in an additional structure in the behavior of the velocity of current-carrying edge states.     

Spin edge helices in a perpendicular magnetic field

We present an exact solution to the problem of the spin edge states in the presence of equal Bychkov-Rashba and Dresselhaus spin-orbit fields in a two-dimensional electron system, restricted by a hard-wall confining potential and exposed to a perpendicular magnetic field. We find that the spectrum of the spin edge states depends critically on the orientation of the sample edges with respect to the crystallographic axes. Such a strikingly different spectral behavior generates new modes of the persistent spin helix-spin edge helices with novel properties, which can be tuned by the applied electric and magnetic fields.     

Scattering by acoustic boundary scatterers with small wave sizes and their reconstruction

The scattering efficiencies of hard and soft cylindrical scatterers are compared using the Novikov-Grinevich-Manakov functional algorithm designed to reconstruct two-dimensional scatterers. The existence of a rigid relationship between the amplitude and phase of the wave scattered by a quasi- point-like scatterer and by scatterers with small wave sizes in the form of a soft cylinder, a soft sphere, and an air bubble in a liquid is confirmed by numerical simulations.     

Photoelectric Properties of Zinc Oxide Films Diffusion-Doped by Gallium and Lithium for Creation of Nonlinear Electric Elements

A technique for local diffusion doping of the certain areas of the ZnO film of donor (Ga) and acceptor (Li) impurities has been developed to produce the films with the topological pattern of doping regions. The diffusion process, electrophysical and photoelectric properties of diffusion-doped samples of the planar MSM structures based on the Al–ZnO–Al, Al–ZnO:Ga–Al and Al–ZnO:Li–Al with the metallic aluminum as contacts are investigated. It is shown that the diffusion introduction of the impurity of gallium suppresses the photosensitivity, and the diffusion introduction of lithium into the ZnO films increases the photosensitivity as compared to the undoped areas of the same film.     

Resonant Multichannel Scattering in a Nanotube with δ-Potentials

The resonant tunneling transmission of an electron through the quantum wire comprising two three-dimensional δ-potentials located along the nanotube axis is considered. Using the formulas obtained recently for amplitudes of multichannel scattering, the condition (equation) of resonance is found for the multichannel scattering, at which the system under consideration becomes completely transparent for motion of the electron. A procedure based on the method of vector diagrams is proposed for simplification of the resonance equation. It is shown that if the initial energy of longitudinal motion is insufficient for excitation of new scattering channels, then the resonance equation coincides with the corresponding equation of one-dimensional problem.     

The second harmonic generation in the symmetric well containing a rectangular barrier

The problem of determination of the maximum of second harmonic generation in the potential well containing a rectangular barrier is considered. It is shown that, in general, the problem of finding the ensemble of structures with equidistant first three levels has two types of solutions. For the first type the second and third energy levels are located above a rectangular barrier, and for the second type the third level is located above the barrier only. It is also shown, that generation corresponding to the second type of solution always is less than generation for the first one. Taking into account the effective mass changes the problem of finding the generation maximum for a finite depth well is exactly solved.     

Photo- and electroluminescence of sulfide and silicate phosphors embedded in synthetic opal

The sulfide (ZnS:Mn, Zn_xCd_1−xS:Mn, Zn_xCd_1−xS:Ag) and silicate (Zn₂SiO₄:Mn) phosphors were synthesized directly inside the pores of synthetic opal by chemical bath deposition. These composites are perfect three-dimensional photonic crystals, which produce effective photo- and electroluminescence at room temperature. The emission spectra are considerably modified by the photonic crystal structure to become anisotropic in accordance with the photonic band gap angular dispersion.     

Sample container temperature gradient influence on the BET specific surface area

Differences between BET specific surface area (BET SSA) values exist due to data collected in stainless steel and less thermally conductive sample holders. Not accounting for the temperature gradient along stainless steel sample holders during manometric gas adsorption measurements at cryogenic temperatures leads to errors of up to 3.2% in the BET SSA values with a relative combined standard uncertainty (RCSU) of 0.63%. A unidimensional heat flow model accurately accounts for the temperature gradient, leading to an agreement of 0.16% between the BET SSA values for both sample holder units.