Selective adsorption of C60 on Ge/Si nanostructures

Selective adsorption of C60 on nanoscale Ge areas can be achieved, while neighboring Si(111) areas remain uncovered, if the whole surface is initially terminated by Bi. Fullerene chemisorption is found at Bi vacancies which form due to partial thermal desorption of the Bi surfactant. The growth rate and temperature dependence of the C60 adsorption were measured using scanning tunneling microscopy and are described consistently by a rate equation model. The selectivity of the C60 adsorption can be traced back to an easier vacancy formation in the Bi layer on top of the Ge areas compared to the Si areas. Furthermore, it is also possible to desorb C60 from Ge areas, allowing the use of C60 as a resist on the nanoscale.     

On the best approximations and Kolmogorov widths of besov classes of periodic functions of many variables

Order estimates are obtained for the best approximations of the classesB _1, ^r in the spaceL _q with 1<q< and classesB _, ^r in a uniform metric. The behavior of Kolmogorov widths of the classesB _p, ^r ,1<p, in the metric of L is studied.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 1, pp. 79–92, January, 1995.     

Refractometry of mechanically compressed RbKSO<Subscript>4</Subscript> crystals

The unit-cell parameters and the spatial symmetry of RbKSO₄ crystals are determined. The temperature and spectral dependences of the refractive indices and birefringence of these crystals are measured. Two first-order phase transitions are found to occur at 116 and 820 K, and the occurrence of isotropic points for three crystallophysical directions is established. The effect of uniaxial stresses on the optical properties of the crystal is studied. Both the birefringence and the birefringence-sign inversion points are found to be rather sensitive to the action of uniaxial mechanical stresses. The temperature-spectral and spectral-baric diagrams of the isotropic state of the RbKSO₄ crystal, as well as the baric shifts of the phase-transition temperatures, are determined.     

Approximative characteristics of the isotropic classes of periodic functions of many variables

Exact-order estimates are obtained for the best orthogonal trigonometric approximations of the Besov (B _p,θ ^r ) and Nukol’skii (H _p ^r ) classes of periodic functions of many variables in the metric of L _q , 1 ≤ p, q ≤ ∞. We also establish the orders of the best approximations of functions from the same classes in the spaces L ₁ and L _∞ by trigonometric polynomials with the corresponding spectrum.     

Yb-doped KY(WO4)2 planar waveguide laser

High-quality monoclinic KY(WO4)2 optical waveguides were grown by liquid-phase epitaxy, and laser operation of an Yb-doped KY(WO4)2 waveguide was demonstrated for the first time to our knowledge. Continuous-wave laser emission near 1 microm was achieved with both surface and buried planar waveguides. An output power of 290 mW was obtained in the fundamental mode and the slope efficiency was above 80%.     

Surface morphology of the Si(310) substrate used for molecular beam epitaxy of CdHgTe: I. Clean Si(310) surface

The effect of vacuum annealing on the morphology of hydrogenated and oxidized Si(310) surfaces is investigated by scanning tunnel microscopy, reflection high-energy electron diffraction, and low-energy electron diffraction. It is found that after desorption of a passivating coating, the surface has a strongly developed profile formed preferentially by steps two monolayers in height. Annealing at a temperature of 900±15°C with subsequent abrupt cooling leads to faceting of the surface by (510) planes. The presence of steps two monolayers in height on the Si(310) surface allows one to use Si crystals oriented along the (310) plane as the substrate for heteroepitaxy of the II–VI compounds.     

Approximation of Classes B p,θ r by Linear Methods and Best Approximations

We investigate problems related to the approximation by linear methods and the best approximations of the classes , 1 p in the space L .     

On Estimates of the Kolmogorov Widths of the Classes $$B_{p,q}^r$$ in the Space Lq

We obtain an order estimate for the Kolmogorov width of the Besov classes of periodic functions of many variables in the space L _q for 2 < p < q < , which complements the result obtained earlier by the author.     

Estimates of the Kolmogorov Widths of Classes of Analytic Functions Representable by Cauchy-Type Integrals. I

In the Banach space of functions analytic in a Jordan domain , we establish order estimates for the Kolmogorov widths of certain classes of functions that can be represented in by Cauchy-type integrals along the rectifiable curve = and can be analytically continued to or to .