Magnetite Nanoparticles in Hybrid Micelles of Polylactide-block-polyethylene Oxide and Sodium Dodecyl Sulfate in Water

Crystallography Reports - Magnetite nanoparticles have been obtained in hybrid micelles of polylactide-block-polyethylene oxide (PL-b-PEO) and sodium dodecyl sulfate (SDS) in a one-stage process....     

Iron contamination in silicon technology

This article continues the review of fundamental physical properties of iron and its complexes in silicon (Appl. Phys. A 69, 13 (1999)), and is focused on ongoing applied research of iron in silicon technology. The first section of this article presents an analysis of the effect of iron on devices, including integrated circuits, power devices, and solar cells. Then, sources of unintentional iron contamination and reaction paths of iron during device manufacturing are discussed. Experimental techniques to measure trace contamination levels of iron in silicon, such as minority carrier lifetime techniques (SPV, μ-PCD, and ELYMAT), deep-level transient spectroscopy (DLTS), total X-ray fluorescence (TXRF) and vapor-phase decomposition TXRF (VPD-TXRF), atomic absorption spectroscopy (AAS), mass spectrometry and its modifications (SIMS, SNMS, ICP-MS), and neutron activation analysis (NAA) are reviewed in the second section of the article. Prospective analytical tools, such as heavy-ion backscattering spectroscopy (HIBS) and synchrotron-based X-ray microprobe techniques (XPS, XANES, XRF) are briefly discussed. The third section includes a discussion of the present achievements and challenges of the electrochemistry and physics of cleaning of silicon wafers, with an emphasis on removal of iron contamination from the wafers. Finally, the techniques for gettering of iron are presented. Received: 16 November 1999 / Accepted: 7 January 2000 / Published online: 5 April 2000     

Topological Laser-Induced Quantum States in Nanocluster Structures: Fundamental Effects and Possible Applications (Electrical and Optical)

Optics and Spectroscopy - Laser-induced nanocluster structures of different types (in topology and in elemental compositions of noble metal/carbon, bimetals, semiconductors, etc.) are studied...     

Electrical properties and recombination activity of copper, nickel and cobalt in silicon

This article combines an extensive literature review of new experimental data on properties of Cu, Ni and Co and their precipitates in silicon with a discussion of experimental data recently obtained by the authors. Special attention is paid to the recombination activity of these metals. It is shown that the recombination activity of Cu, Ni, Co and their complexes is low in p-type Si, compared to that of other transition metals such as iron. However, it increases markedly upon formation of precipitates or decoration of existing lattice defects. This is explained by the formation of a precipitate-related defect band and of an attractive potential for minority charge carriers by the charged precipitates. The role of Cu, Ni and Co in the degradation of multicrystalline solar cells efficiency is discussed in a separate section. It is suggested that recently reported intragranular microdefects, which decrease the lifetime of solar cells, may be microprecipitates of these metals. Received: 18 September 1997/Accepted: 25 September 1997     

Perimidine in the hetarylation reaction

Indoles and pyrroles were hetarylated by perimidines in the presence of benzoyl chloride. N-Acyl derivatives of 2-indolyl(pyrrolyl)-2, 3-dihydroperimidine were synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1685, December, 1976.     

Progress in the Design of New Photonics and Optoelectronics Elements Using Advantages of Contemporary Femto-Nanophotonics

We consider experimentally and theoretically the detection of quantum states in nanocluster semiconductor/metal structures upon the registration of hopping/tunneling electrical conductivity and possible mechanisms of realization of such states. We obtain nanostructured thin films on the substrates using different technologies, including laser ablation of solid surfaces. We show that it is possible to control the properties of the films by varying the topology of such synthesized systems. We analyze the features arising due to the specific conductivity of granular media revealed by the measured current–voltage characteristics and electrical resistance dependences for nanocluster bimetallic films of different compositions.     

Syntheses and properties of novel non-ionic fluorinated multichains “star-like” surfactants

A series of star-like nonionic surfactants (with two hydrophobic and two hydrophilic chains) with different lengths of hydrophilic and hydrophobic arms were synthesised on the basis of pyromellitic acid dianhydride. The hydrophilic arms were formed by polyoxyethylene and hydrophobic ones either by perfluoro- or by alkyl chains. The adsorption monolayers (Gibbs monolayers) were studied by surface pressure (π) measurements as a function of time for different surfactant concentrations. For the spread monolayers (Langmuir monolayers), the measurements of the surface pressure (π) versus the molecular area (A) as well as the relaxation measurements of the area (A) as a function of time at constant surface pressure were performed. The comparison between the characteristic parameters of two types of monolayers was made in order to understand the effect of the preparation conditions on the structure of these monolayers.It was found that decreasing the fluoroalkyl chain length induced a systematical decrease in the stability of Langmuir monolayers, which is manifested as the Marangoni-Gibbs viscoelasticity of the monolayers. For the surfactants, which have a large number of oxyethylene groups, adsorption at the air/water interface from the bulk solution required extremely long times to reach equilibrium due to the diffusion from the solution and to the conformational rearrangements at the interface. The observation of a hysteresis in the compression/decompression curves for these compounds is explained by the presence of the residual organic solvent molecules absorbed by oxyethylenic chains. A novel model describing the kinetics of desorption or rearrangement of molecules during the lateral compression was suggested, allowing the estimation of both characteristic time of this process and areas per molecule at the equilibrium from the relaxation curves A(t).     

Amphiphilic Linear-Branched Copolylactides and Disperse Systems on Their Basis

The linear-branched copolylactides containing linear side poly(ethylene oxide) blocks are synthesized and characterized. The critical micelle concentrations and the aggregative stability and the dispersity of oil/water emulsions stabilized by these copolymers are estimated. The polylactide microparticles are obtained by emulsification followed by evaporation of an organic solvent using acetylsalicylic acid as a model drug. The structure of copolylactides strongly affects the properties of the microparticles. On one hand, the presence of large poly(ethylene oxide) blocks in the linear-branched macromolecules leads to the formation of colloidal systems with a higher aggregative stability of emulsions and a lower size of particles, and on the other hand, the microparticles formed from these copolymers possess a lower incorporation efficiency relative to water-soluble low-molecular-mass compounds and the profile of the release of these compounds is nonlinear and contains the region of accelerated release.     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.