Lu, Gd codoped KY(WO(4))(2):Yb epitaxial layers: towards integrated optics based on KY(WO(4))(2)

Codoping KY(WO(4))(2):Yb layers with optically inert Lu and Gd ions allows a large increase of the refractive index contrast with respect to KY(WO(4))(2) substrates. This paves the way for the realization of integrated optical circuits based on this very promising material. First riblike waveguide structures have been fabricated and propagation losses below 1 dB/cm have been evaluated. A Y-junction with a splitting ratio close to 1:1 and additional losses of 1.4 dB has also been demonstrated.     

Electrical properties of water drops inside the dropwise cluster

The Letter shows that inside a dropwise cluster formed over the heated water surface, water drops are electrically charged. The charge of a separate drop reaches 10³ units of an elementary charge. The drops are positioned from each other at the distance of double Debye radius length. It is fixed up that drops levitate over the water surface in consequence of the Stokes force acting from the side of gas-vapor flow rising from water surface. The Stokes force thousand times exceeds the Coulomb drop repulsion force from the water surface.     

Layer-resolved photoelectron diffraction from Si(0 0 1) and GaAs(0 0 1)

Photoelectron diffraction in the layer-resolved mode brings more detailed information about local atomic arrangement than is obtained in the standard mode. This is demonstrated in crystals with diamond and zinc-blende structures, both for unpolarized photon excitation as well as for circularly polarized excitation. The full angular distributions of photoemission intensities are evaluated for large atomic clusters representing ideally truncated surfaces of Si(0 0 1) and GaAs(0 0 1). Highly structured layer-resolved patterns enable a more detailed understanding of the standard mode outcomes. Photoelectron intensities from atomic layers placed at different depths under the crystal surface provide direct evidence about electron attenuation and its anisotropy in crystals.     

Optical properties of the ternary compound Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se:Co

We present the results of experimental studies of the optical properties of cobalt-doped Cd _x H_1−x Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·10¹⁸, 5·10¹⁹, and 1·10²⁰ cm⁻³ at T = 90 K and 300 K. The composition (x = 0.18) of the Cd _x Hg_1−x Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations N_Co < 5·10¹⁸ cm⁻³. For N_Co ∼ 5·10¹⁸ cm⁻³, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007.     

Theoretical and experimental determination of the initial stage of plastic relaxation of misfit stresses in a (111) substrate-film islands heterosystem

A model for determining the critical thickness of a film h _c is developed to introduce misfit dislocations in the slip planes of a film and a substrate parallel to the interphase boundary (111). Experimental values h _c that agree with calculated values are determined for the Ge/Si(111) and Si₃N₄/Ge(111) heterosystems. The two-level epitaxial growth of Ge on Si is attained in the regime of combining the step-layer and 2D island growth mechanisms.     

Synthesis and Transformations of 2-Hydroxy-3-arylazo-1,4-naphthoquinones

A series of 2-hydroxy-3-arylazo-1,4-naphthoquinones were prepared by coupling of 2-hydroxy-1,4-naphthoquinone with aryldiazonium chlorides. The reactivity of the products toward electrophilic and nucleophilic agents was studied. In reaction with o-phenylenediamine they give condensation products, the corresponding benzo[a]phenazines.     

Synthesis of benzoquinone derivatives containing benzotriazole fragments

2,3,5,6-Tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone was synthesized in 85% yield by reaction of 2,3,5,6-tetrachloro-1,4-benzoquinone with 1H-benzotriazole in pyridine at room temperature. Treatment of 2,3,5,6-tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone with piperidine, ω-amino acids, and aromatic amines gave the corresponding 2,5-diamino-3,6-bis(1H-benzotriazol-1-yl)-1,4-benzoquinones.