V. V. Vasil’ev

Features of Magneto-Optical Resonances in an Elliptically Polarized Traveling Light Wave

The parameters of nonlinear absorption magneto-optical resonances in the Hanle configuration have been studied as functions of the ellipticity of a traveling light wave. It has been found that these parameters (amplitude, width, and amplitude-to-width ratio) depend strongly on the polarization of the light wave. In particular, the resonance amplitude can increase by more than an order of magnitude when the polarization changes from linear to optimal elliptic. It has been shown that this effect is associated with the Doppler frequency shift for atoms in a gas. The theoretical results have been corroborated in experiments in Rb vapor.

Capacitance-voltage characteristics of the p-Cd0.27Hg0.73Te-based structures with a wide-gap graded-gap surface layer

Capacitance-voltage characteristics of the structure In-SiO2-(graded-gap layer Cd0.71–0.27Hg0.29–0.73Te)-p-Cd0.27Hg0.73Te-GaAs are investigated at temperatures of 80 K and higher. The characteristics have the hysteresis, specifically, the characteristic is similar to a forward portion of the usual high-frequency characteristic (from enrichment to inversion), while the reverse portion has an extended plateau, in which the capacitance of the space-charge region is larger by a factor of approximately 2. To interpret the capacitance-voltage characteristic, the effect of partial screening of the graded-gap part of the space-charge region from the electric field of the test signal, as well as the effect of formation of the potential electron well near the surface due to the recharging of donor levels are considered.

Charge transport in HgCdTe-based n+-p photodiodes

It is shown that dark currents measured at 77 K in Hg1−xCdxTe (x⋍0.21) homojunctions can be adequately described by the balance equations with allowance made for the two main charge-transport mechanisms, i.e., tunneling assisted by traps in the band gap and recombination via these traps; the above homojunction may find application in microphotoelectronics in the infrared spectral range of 8–12 µm. Other charge-transport mechanisms are included in the consideration as additive terms. A comparison between the experimental current-voltage characteristics and dynamic resistance of HgCdTe diodes with the results of calculations was carried out. A good agreement was obtained between experimental data and the results of calculations, in which the donor and acceptor concentrations in the n and p regions of diodes, the concentration of traps and the position of their levels in the band gap, and the lifetimes of charge carriers for recombination via these traps were used as adjustable parameters.

High-performance 320 × 256 long-wavelength infrared photodetector arrays based on CdHgTe layers grown by molecular beam epitaxy

This paper gives the parameters of 320 × 256 element long-wavelength infrared photodetectors fabricated by a new improved technology based on heteroepitaxial mercury-cadmium-tellur structures. In these photodetectors, the variation of the photodiode bias voltage over the area of the array is minimized; inefficient photodiode regions related to both hybridization and spike-shaped growth defects of epitaxial films are eliminated; the current-voltage characteristics of the diodes in the resulting photodetectors are homogeneous and are limited by the diffusion current component up to −400 mV. The dark current is 0.25–0.45 nA, and R0A = (0.6–3) · 102 Ω · cm2. The voltage sensitivity, the threshold irradiance, and the average NETD at the maximum sensitivity are 11.8 · 108 V/W, 3.7 · 10−8 W/cm2, and 26.8 mK, respectively. The percentage of defective elements is 1.5%.

Effect of the functionality of junctions on the elasticity of polymacromonomer networks: Computer simulation

The elastic properties of polymer networks formed via the radical polymerization of macromonomers with two polymerizable end groups are studied via computer simulation. It is shown that variation in the average functionality of network junctions, f avg, in a wide range (∼5–55) leads to a significant change in the shear modulus of the network. According to experiments with real networks (gels of poly(ethylene oxide) macromonomers), the shear modulus increases as f avg increases. This effect is not due only to a decrease in the fluctuations of positions of network junctions. The main cause of the increase in the modulus is that the modulus component due to interaction between polymer chains (entanglements) increases as the functionality of junctions in the investigated networks increases. The conclusion is made that these networks gain entanglements during the formation of network junctions with high functionality rather than inherit them from the solution of macromonomer chains.

Dual structure of saturated absorption resonance at an open atomic transition

Experiments on open transitions of the D1 line of alkali metals (Cs and Rb isotopes) reveal the dual structure of saturated absorption resonance in the signal of a high-intensity optical wave in the presence of a low-intensity counterpropagating wave. Theoretical analysis shows that the observed shape of the resonance is associated with the openness of the atomic transition as well as with the Doppler effect for atoms in a gas. The results are of general physical significance for nonlinear spectroscopy and can also find application in metrology (frequency and time standards on open transitions).

Selective cyclometalation of disubstituted acetylenes and ethylene with diethylmagnesium and ethylmagnesium halides in the presence of zirconium complexes

Catalytic cyclometalation of disubstituted acetylenes and ethylene with ethylmagnesium halides EtMgHlg (Hlg = Cl, Br) and diethylmagnesium Et2Mg in the presence of Cp2ZrCl2 gave tetrasubstituted magnesacyclopenta-2,4-dienes and disubstituted magnesacyclopent-2-enes. A probable scheme of formation of cyclic unsaturated organomagnesium compounds was proposed, according to which the reactive intermediates in the cyclometalation process are zirconacyclopentadienes and zirconacyclopentenes generated from Cp2ZrCl2, EtMgHlg, Et2Mg, acetylenes, and ethylene.

Field-dependent photosensitivity of In-SiO2-Cd0.28Hg0.72Te metal-insulator-semiconductor structures with an opaque field electrode

The study of the photosensitivity of an In-SiO2-Cd0.28Hg0.72Te metal-insulator-semiconductor structure with an opaque electrode is continued and the results are reported in this paper. The effect of a drastic decrease in photosensitivity with increasing inversion voltage is considered. This effect manifests itself both under unmodulated illumination (measurements of photocapacitance) and under modulated illumination (measurements of photovoltage), with the onset of a decrease in photovoltage coming ahead of that in photocapacitance. It is believed that this effect is caused by an increase in the longitudinal resistance of the inversion layer and by the anomalous generation of charge carriers at the semiconductor-insulator interface; as a result of the latter, the resistance of the induced p-n junction decreases.

Investigation of a change in the chemical composition of the surface of CdxHg1−xTe samples as a result of treatment by N2O and H2 gases activated in a high-frequency discharge

A change in the chemical composition of the CdxHg1−xTe surface as a result of its treatment by atomic beams of oxygen and hydrogen was investigated. The beams were obtained by the electron impact in a high-frequency plasma of N2O and H2 gases. The consecutive action of beams of atomic oxygen and hydrogen was shown to result in the removal of carbon-containing compounds, a layer of native oxide, and tellurium in its elemental state from the surface of samples.

The Hall effect in La0.67Ba0.33MnO3

The Hall effect in polycrystalline barium-substituted lanthanum manganite La0.67Ba0.33MnO3 has been investigated in the temperature interval 298<T<355 K. It is found that the anomalous Hall coefficient in this material is two orders of magnitude greater than the normal coefficient. At T0=333 K the normal Hall coefficient changes sign, which indicates a change in the type of conductivity. The temperature dependence of the normal Hall coefficient, electrical conductivity, and magnetoresistance is explained on the basis of the concept of motion of the mobility edge attendant as the temperature changes.