Remote-doping scattering and the local field corrections in the 2D electron system in a modulation-doped Si/SiGe quantum well

The small, about 30% magnetoresistance at the onset of full spin polarization in the 2D electron system in a modulation-doped Si/SiGe quantum well gives evidence that it is the remote doping that determines the transport scattering time. Measurements of the mobility in this strongly-interacting electron system with remote-doping scattering allow us to arrive at a conclusion that the Hubbard form underestimates the local field corrections by about a factor of 2.     

The Role of Active Oxygen Transfer through the Gas Phase in Propylene Oxidation over a Bismuth–Molybdenum Catalyst

The transfer of atomic oxygen from the surface of bismuth oxide onto molybdenum oxide through the gas phase, including the case when ozone was fed to the catalyst bed, is experimentally studied. It is found that the transfer of atomic oxygen through the gas phase only leads to the formation of the products of complete oxidation of propylene under conditions of heterogeneous propylene oxidation on the mixture of molybdenum and bismuth oxides. No new sites are formed on the surface of molybdenum oxide.     

Modification of the MgO–Al2O3–TiO2–SiO2 Glass by Silver Diffusion for the Formation of Luminescent Molecular Clusters

Doklady Chemistry - The capabilities of diffusion treatment of alkali-free MgO–Al2O3–TiO2–SiO2 glass using Ag-containing salt melts or special pastes for the formation of...     

Polarization field in a single-valley strongly-interacting 2D electron system

The magnetic field of complete spin polarization is calculated in a disorderless single-valley strongly-interacting 2D electron system. In the metallic region above the Wigner-Mott transition, nonequilibrium spin states are predicted, which should give rise to hysteresis in the magnetization.     

Giant growth of quantum oscillations in an inhomogeneous 2D electron system

It is detected experimentally for the first time that the connection of 2D electron systems with different electrochemical potentials results in long-range (τ 50 μm) electron density disturbances. When a gated region of a Corbino sample is strongly depleted, the amplitude of the magnetoresistance oscillations caused by high density ungated regions is found to increase in direct proportion to the sample resistance, which is dominated by low-density regions with small conductivity. Experiments on samples with an artificial potential profile (antidots and etched rings) below the gate show that the observed effects are not due to contact effects. Pis’ma Zh. Eksp. Teor. Fiz. 63, No. 1, 55–60 (10 January 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Variation of the dispersity and phase composition of a ferrous oxide catalyst in the burning of an ammonium perchlorate-polymethylmethacrylate mixture

Products of conversion of the ferrous oxide catalyst collected from the burning region of an AP-PMMA mixture show the significant aggregation of the catalyst, with large (40–50 m) spherical particles having a metallic glitter. Significant variations in the phase composition are observed, Fe₃O₄·-Fe₂O₃ solid solution and tetragonal and monoclinic Fe₂O₃ being formed.

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- a-Fe₂O₃ . . ( 40–50 ) . : Fe₃O₄·-Fe₂O₃, Fe₂O₃.

     

Planar detectors for multielement systems of millimeter-wave imaging

We discuss the concept of developing a millimeter-wave multielement matrix receiver on the basis of planar antennas with directly coupled low-barrier Schottky diodes. Three main problems are considered which involve choosing and developing a design of the planar antenna coupled with the low-barrier Schottky diode, optimizing the parameters of the low-barrier Schottky diodes for obtaining maximum sensitivity, and ensuring compact arrangement with weak mutual influence of the planar detectors in a two-dimensional array. We propose a design of the slot antenna with an active resistance of about 800 Ω at a resonant frequency of 94 GHz. The detection characteristics of diodes with the differential Schottky-barrier resistance in the range R_j = 0.4–1000 kΩ for a zero bias are studied experimentally. The mutual influence of the neighboring antennas is examined for developing the multielement radio-imaging system. The conditions of weak cross influence of the closely located planar detectors are determined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 12, pp. 1077–1087, December 2007.     

Fracton vibrations in vitreous SiO2 as revealed from Raman spectroscopy study

Low-frequency Raman spectroscopy is used to study the sensitivity of the dynamic (vibrational) properties of the fractal structure of nanocracks in vitreous SiO₂ to the mechanical and thermal previous history of the sample. The material is obtained by vacuum-compression fritting of the sol-gel synthesis products. After fritting, continuity defects having a nanostructural scale and possessing fractal geometry are left at the site of microcracks in the course of preliminary mechanical processing of the sample. The features of such defects are an absence of the boson peak in the Raman spectrum and a monotonic decrease of the intensity according to the law of light scattering from acoustic vibrations of fractals. The conditions for the emergence of the fractal structure and its dependence on the rigidity of the walls of nanocracks are determined from the scattering mode.