Structure and composition of nanotubes formed during the anode oxidation of titanium

The structure and composition of nanotubes ≈1.5 μm long and ≈100 nm in diameter, formed electrolytically on the surfaces of titanium plates in a two-electrode cell at room temperature in a 0.5 wt % NH4F solution in ethylene glycol and glycerin, were studied by analytical and diffraction transmission electron microscopy.     

Radiation of a Resonant Medium Excited by a Periodically Phase-Modulated Laser in the Regime of Strong Coupling between the Field and the Matter

Optics and Spectroscopy - The radiation of a two-level resonant medium that is placed into a cavity and is excited by a periodically phase modulated laser pulse is studied theoretically. The...     

Visible Luminescence of SiGe/Si Quantum Wells Under an External Anisotropic Deformation

We realize for the first time an experimental investigation of the IR and visible luminescence of SiGe/Si heterostructures with quantum well subjected to an external anisotropic deformation. We show that tensile strain along the [100] direction enhances the absolute and relative intensities of visible luminescence by a factor of 7/3 at a temperature of 5 K. This effect is absent for a tensile strain along the [110] direction. We explain the phenomenon observed in view of the model of single-photon biexciton recombination for the system in which the bottom of the conduction band is formed by only two opposite electronic valleys.     

Visible luminescence enhancement methods in SiGe/Si heterostructures

The possibility of increasing the photoluminescence signal of Si1?xGex/Si quantum wells in the visible spectral range due to a change in the conduction band structure and the interaction of many-body states with plasma oscillations of metal nanoparticles is studied. The sample band structure was controlled using a uniaxial strain of ～10?4. It is found that such an approach allows an increase in the emission intensity of biexcitons in the quantum well (x = 9%) by a factor of 2.4 at a temperature of 5 K. Metal nanoparticles deposited on the sample surface with a protective layer thickness of 20 nm allowed us to increase the luminescence intensity of quantum wells approximately by a factor of 2.7.     

Scattering of nonequilibrium acoustic phonons in coarse-grained pure ZnSe with random microtwin structure

Propagation of nonequilibrium acoustic phonons in a coarse-grained ZnSe produced through chemical synthesis from a vapor phase was studied for phonons generated optically or by a metallic heater. The material is characterized by a microtwin structure in randomly oriented grains. Phonon transport studies, in combination with low-temperature photoluminescence, optical and electron microscopy, and x-ray diffraction analysis, made it possible to establish the decisive role played by extended defects in scattering of high-frequency acoustic phonons in this matterial.     

Nonstandard Features of the Interaction of Single Luminescent Centers Formed by Partial Dislocation Cores in CdTe and ZnSe with Longitudinal Optical Phonons

JETP Letters - Low-temperature (5 K) microphotoluminescence has been measured in order to study individual luminescent centers formed by the cores of partial dislocations in a CdTe/Si film and a...     

Frequency stability and reproducibility of the 3.39 μm He−Ne laser stabilized on the methane line

Physical factors determining the frequency reproducibility of a gas laser with nonlinear absorption are analyzed. On the basis of experimental and theoretical results it is shown that the collisional shift, the second-order Doppler effect, the recoil effect, and the magnetic hyperfine structure do not reprsent the limitation in achieving a frequency reproducibility of the order of 10^?13?10^?14. This paper reports on experiments achieving frequency stability of 5·10^?15 and reproducibility of 3·10^?14 for the 3.39 μm He?Ne laser with an internal methane cell.     

Optical and electrophysical properties of defects in high-purity CdTe

The electronic spectrum of defects formed in low-temperature synthesis and growth of high-purity CdTe[111]from the vapor phase of the starting components has been studied by the photoluminescence and photoconductivity methods, as well as using the analysis of the behavior with temperature of the conductivity. The studies have revealed in the crystals, in addition to the comparatively shallow centers involving primarily donors and acceptors contained in residual substitutional impurities, deep acceptor states with activation energies of 0.25, 0.60, and 0.86 eV, which differ in the character and magnitude of the localizing potential. While the deep centers at 0.60 and 0.86 eV display strong localization of electronic states, the center with the 0.25-eV activation energy is associated with defects for which the major part of the localizing potential extends uniformly in space over several unit cells. Such centers are assumed to originate from twinning-induced extended defects.