Search Results - (Author, Cooperation:A. Zhukov)

2018-09-15

American Physical Society (APS)

1098-0121

1095-3795

Physics

Semiconductors II: surfaces, interfaces, microstructures, and related topics

2018-09-15

American Physical Society (APS)

1098-0121

1095-3795

Physics

Semiconductors II: surfaces, interfaces, microstructures, and related topics

2018-11-03

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-11-03

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2011-08-13

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2018-11-15

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2012-12-04

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Fluorescence Resonance Energy Transfer ; *Models, Molecular ; Protein Binding ; Protein Structure, Tertiary ; Ubiquitin/*chemistry/*metabolism

2018-05-10

Institute of Physics Publishing (IOP)

1748-0221

Physics

2018-10-03

Institute of Physics Publishing (IOP)

1748-0221

Physics

1089-7550

AIP Digital Archive

Physics

Mn and Cr powders were produced from electrolytic Mn and Cr by ball milling in a stainless steel container with carbon steel balls. The milling time, t, varied from 5 min to 8 h. Structures were investigated by x-ray and electron microscopy. Chemical compositions of samples were checked by flame atomic absorption spectrometry. The magnetization was measured by induction method in a pulsed magnetic field up to 10 T. The main part of Mn and Cr powder volume was occupied by α-Mn and b.c.c. Cr, respectively. Diffraction peaks became vaster and more asymmetric with increasing t due to the onset of defects of the structure. The presence of MnO was observed in the Mn sample after 8 h of milling. The size of Mn and Cr particles over same critical t (for chromium t=100 min) was no more than 1 mm. A noticeable Fe content, which increases at higher t, was observed. The Mössbauer spectra of Cr and Mn samples showed the lines of α-Fe and γ-Fe. High values of saturation magnetization, σ, up to 5.4 emu/g, and susceptibility and existence of the hysteresis in low fields at temperatures up to 360 K, indicate ferromagnetic ordering of the samples. Within the range of 78–360 K σ only slightly depends on temperature, but noticeably grows with increasing t at fixed temperature in Cr powders, remaining practically constant in Mn powders. No correlation could be observed between Fe content and σ : the latter remained the same in Mn with Fe concentration increasing, but in Cr, as Fe concentration increased sevenfold, it grew by four times. Spontaneous magnetization per mass unit of Fe, σ, was sufficiently lower than that of pure α-Fe (220 emu/g). The obtained values of σ correspond neither to Fe solid solution nor to pure Cr or Mn. Elucidation of the obtained results can be done both by the presence of α-Fe particles and by variation of exchange interactions caused by sample defects. A noticeable difference of σ values from those properties of bulk α-Fe can be explained by γ-Fe availability and grinding of particles being smaller than single domain sizes.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The effect of both thermal treatments as well as chemical etching treatments on the magnetic behavior has been investigated in nearly-zero magnetostriction glass-coated amorphous (Co1−xMnx)75Si10B15 (x=0.08, 0.09, and 0.10) microwires. Such a small change in x results in rather strong changes in the hysteresis loop parameters including coercitivity, Hc, and initial magnetic permeability, μ15. This effect was ascribed to the change of sign of the magnetostriction constant with a proper combination of the coercivity and relatively high initial permeability for the as-cast x=0.09 sample. Thermal treatment (temperatures 100–200 °C for 0.5–2 h) as well as chemical etching in 20% diluted fluoridric acid with duration from 0.5 up to 50 min modify this magnetic parameters owing to the internal stresses relaxation process. In particular, annealing under applied magnetic field (field annealing) can improve more significantly these magnetic parameters: increasing both Hc and μ15. Such phenomenology can be interpreted considering the noticeable longitudinal magnetic anisotropy induced by the combined effects of the magnetic field and strong internal stresses arising from the coating during the thermal treatment. The reduction of the glass coating thickness by chemical etching leads to a decrease of the internal stresses from a coating and, consequently, to a decrease of the transverse magnetoelastic anisotropy. Such decrease of anisotropy plays a role similar to that induced by field annealing on the hysteretic behavior. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Quantum dots (QDs) formed on GaAs(100) substrates by InAs deposition followed by (Al,Ga)As or (In,Ga,Al)As overgrowth demonstrate a photoluminescence (PL) peak that is redshifted (up to 1.3 μm) compared to PL emission of GaAs-covered QDs. The result is attributed to redistribution of InAs molecules in the system in favor of the QDs, stimulated by Al atoms in the cap layer. The deposition of a 1 nm thick AlAs cover layer on top of the InAs–GaAs QDs results in replacement of InAs molecules of the wetting layer by AlAs molecules, leading to a significant increase in the heights of the InAs QDs, as follows from transmission electron microscopy. This effect is directly confirmed by transmission electron microscopy indicating a transition to a Volmer–Weber-like QD arrangement. We demonstrate an injection laser based on this kind of QDs. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The Taylor–Ulitovski technique has been successfully employed to fabricate glass-coated microwires having internal nucleus made of alloys of various immiscible elements. Series of alloys CoxCu100−x, Co29Ni25Mn1Cu45, and (FeSiBC)50Cu50 have been studied from structural and magnetic points of view. The influence of thermal treatments on the structure and magnetic properties has been moreover studied with a final aim to obtain such type of microwires with enhanced hard magnetic properties. A maximum coercivity of around 750 Oe is achieved in the optimum conditions. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report resonant luminescence studies in ultrathin InAs quantum-well structures. Under double resonant conditions, sharp lines induced by longitudinal optical phonons were observed in the emission spectrum, in addition to the broad band luminescence. These sharp lines exhibited moderate circular polarizations whereas the linear polarization was negligible, indicating a resonant luminescence process. The properties of these sharp lines observed in InAs monolayer quantum wells are quite different from those observed previously in GaAs-AlxGa1−xAs quantum wells under similar conditions. InAs phonons were found to participate in the exciton resonant scattering process at high magnetic fields where double resonant conditions are fulfilled. InAs-like phonon energy is determined to be close to 29.9 meV, in good agreement with the energy expected for a uniform ultrathin elastically strained InAs layer. We performed various circular and linear polarizations to investigate the resonant luminescence process in thin InAs layers inserted in GaAs. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

InAs self-organized quantum dots inserted in InGaAs quantum well have been grown on GaAs substrates by molecular beam epitaxy. The lateral size of the InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases. The quantum dot emission wavelength can be controllably changed from 1.1 to 1.3 μm by varying the composition of the InGaAs quantum well matrix. Photoluminescence at 1.33 μm from vertical optical microcavities containing the InAs/InGaAs quantum dot array was demonstrated. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A 1 W continuous-wave laser operation via the ground state of vertically coupled InGaAs quantum dots (VCQDs) in an AlGaAs matrix is demonstrated. VCQDs are directly revealed in transmission electron microscopy images of the laser structure. Ninety-six percent internal quantum efficiency is realized. The laser gain maximum shifts significantly with drive current towards higher photon energies in agreement with the relatively broad size distribution of VCQDs. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We present gain measurements and calculations for InAs/GaAs quantum dot injection lasers. Measurements of the modal gain and estimation of the confinement factor by transmission electron microscopy yield an exceptionally large material gain of 6.8(±1)×104 cm−1 at 80 A cm−2. Calculations including realistic quantum dot energy levels, dot size fluctuation, nonthermal coupling of carriers in different dots, and band filling effects corroborate this result. A large maximum differential gain of 2×10−12 cm2 at 20 A cm−2 is found. The width of the gain spectrum is determined by participation of excited quantum dot states. We record a low transparency current density of 20 A cm−2. All experiments are carried out at liquid nitrogen temperature. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Annealing at higher temperature (700 °C) of structures with two-dimensional and three-dimensional arrays in InAs–GaAs quantum dots (QDs) results in an increase in the size and in a corresponding decrease in the indium composition of the QDs. The change in the In composition is monitored by the contrast pattern in the plan-view transmission electron microscopy (TEM) images viewed under the strong beam imaging conditions. Increase in the size of the QDs is manifested by the plan-view TEM images taken under [001] zone axis illumination as well as by the cross-section TEM images. We show that the dots maintain their geometrical shape upon annealing. Luminescence spectra demonstrate a shift of the QD luminescence peak toward higher energies with an increase in the annealing time (10–60 min) in agreement with the decrease in indium composition revealed in TEM studies. The corresponding decrease in the QD localization energy results in an effective evaporation of carriers from QDs at room temperature, and the intensity of the QD luminescence decreases, and the intensity of the wetting layer and the GaAs matrix luminescence increase with the increase in the annealing time. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We study the optical properties of structures composed of stacked InAs submonolayer insertions in an AlGaAs matrix grown on a GaAs(100) surface. The increased refractive index in the active region necessary for waveguiding is caused by the absorption peak due to excitons trapped by monolayer-height InAs islands. Despite a very low average InAs concentration, a thin AlGaAs buffer layer and an absorbing GaAs substrate photopumped lasing in the visible spectral range is already realized at low excitation density. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report on optical studies of relaxation processes in self-organized InAs/GaAs quantum dots (QDs). Near resonant photoluminescence excitation spectra reveal a series of sharp lines. Their energy with respect to the detection energy does not depend on QD size and their energy separations are close to the InAs LO phonon energy of 32.1 meV estimated for strained pyramidal InAs QDs. The shape of the PLE spectra is explained by multiphonon relaxation processes involving LO phonons of the QD as well as of the wetting layer, an interface mode, and low frequency acoustical phonons. © 1996 American Institute of Physics.

Electronic Resource