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Two-dimensional Array (two-dimensional + array)
Selected AbstractsFabrication of Two-Dimensional Arrays of CdSe Pillars Using E-Beam Lithography and Electrochemical DepositionADVANCED MATERIALS, Issue 1 2003Y.-W. Su Two-dimensional arrays of high refractive index structures can be fabricated using a combination of e-beam lithography for pattern definition and electrochemical deposition for structure formation. The potential of this method is demonstrated for CdSe, where nanopillars, mushrooms (see Figure), walls, and crosses are prepared. Such arrays have potential in optical device applications such as photonic crystals and waveguides. [source] A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004Yanbin Wang A new diffraction technique for combined angle- and energy-dispersive structural analysis and refinement (CAESAR), by collecting angle-dispersive data using a solid-state detector (SSD) and white synchrotron radiation, is introduced. By step scanning a well calibrated SSD over a limited 2, range, a series of one-dimensional energy-dispersive data (intensity versus energy) are obtained as a function of 2,. The entire intensity (Int) data set consists of several thousand channels covering a range of photon energies, E (up to ,150,keV), at each of the ,1000 2, steps, forming a 2,4 mega-element two-dimensional array, Int(E, 2,). These intensity data are then regrouped according to photon energies, which are defined in the multichannel SSD as individual channels, yielding a large number of intensity versus 2, (angle-dispersive) data sets, Int(E = const., 2,), each of which corresponds to a given photon energy or wavelength. The entire data set, selected subsets or composite scans can be used for multiple data set Rietveld refinement. Data collected both on ,-Al2O3 (a NIST diffraction standard) at ambient conditions and on a mixture of MgO and Au at high pressure were analyzed using the Rietveld technique, with varying schemes of data treatment. Furthermore, it is demonstrated that data within certain energy bands (,E/E = ±10%) may be binned together to improve counting statistics in a composite angle-dispersive scan, even when collected with much coarser scan steps of 0.1 or 0.2°. This technique is useful for high-pressure as well as general purpose powder diffraction studies that have limited X-ray access to the sample using synchrotron radiation. Several advantages are discussed. [source] Microwave Bandgap in Multilayer Ceramic StructuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Bo Li A multilayer ceramic structure with a photonic bandgap (MC-PBG) was fabricated by a method of tape casting combined with screen printing. The MC-PBG structure is a two-dimensional array with either rectangular or hexagonal metal coils in a ceramic matrix. The metal coils are connected to the base metal layer in the ceramic substrate to form a monolithic body. The surface-wave dispersion properties of these MC-PBG structures were measured. A stop band, which is significantly influenced by the symmetrical characteristics of the inductor,capacitor (LC) arrays, was found in both the structures in the frequency range of 2.0,3.5 GHz. Because of their effective surface-wave suppression, MC-PBG structures can be used as high-performance antenna substrates to enhance the broadside gain of patch antenna devices. [source] Hopping photoconductivity and its long-time relaxation in two-dimensional array of Ge/Si quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005N. P. Stepina Abstract Photoconductivity excitation kinetics has been studied in a two-dimensional array of Ge/Si quantum dots under illumination with different light wavelength. Both negative and positive photoeffects depending on dot occupations with holes were observed. Long-time conductivity dynamics (typically, 102,104 sec at T = 4.2 K) has been revealed as well as after switch on and switch off the illumination, displaying a sluggish temporal dependence. The observed effects were not suppressed by decreasing of the excitation energy below the silicon band-gap. For electronic glasses it was discovered that the more time under excitation the faster relaxation rate. Our results are explained by the different capture rate of electrons and holes by quantum dots, due to the presence of potential barriers created by positively charged Ge quantum dots. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two isomorphous cobalt(II) complexes: poly[[diaqua-,-2,5-dicarboxybenzene-1,4-dicarboxylato-,-1,2-di-4-pyridylethene-cobalt(II)] 1,2-di-4-pyridylethene solvate] and the 1,2-di-4-pyridylethane analogueACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Ana María Atria The two isomorphous title structures, formulated as {[Co(C10H4O8)(C12H10N2)(H2O)2]·C12H10N2}n, (I), and {[Co(C10H4O8)(C12H12N2)(H2O)2]·C12H12N2}n, (II), respectively, are reported. They crystallize in the space group P with only one formula unit in the asymmetric unit, so that the organic ligands lie about inversion centres and the Co atom lies on an inversion centre. The Co atoms are octahedrally coordinated by a carboxylate O atom from 2,5-dicarboxybenzene-1,4-dicarboxylate (H2btc), one N atom from 1,2-di-4-pyridylethene (L) in (I) or from 1,2-di-4-pyridylethane (L) in (II), and one coordinated water molecule, plus their inversion-related species. This particular coordination results in a two-dimensional array, with an elemental unit in the shape of a parallelogram having the CoII cations at the corners, linked in one direction by L bridges and in the opposite direction by H2btc groups. The L solvent molecules act as pillars between parallel planes, linking them by strong hydrogen bonds where the H atoms lie midway between the formal donor/acceptor atoms in a `shared' mode. Comparison is made with structures presenting the same structural motif, strongly suggesting that the two-dimensional arrangement reported here might be a very stable robust building block for molecular engineering purposes. [source] Synthesis, structural characterization and cytotoxic activity of diorganotin(IV) complexes of N -(5-halosalicylidene)tryptophaneAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2009Laijin Tian Abstract Four new diorganotin(IV) complexes of N -(5-halosalicylidene)tryptophane, R2Sn[5-X-2-OC6H3CHNCH(CH2Ind)COO] [Ind = 3-indolyl; R, X = Et, Cl (1); Et, Br(2); n -Bu, Cl (3); n -Bu, Br (4)], were synthesized and characterized by elemental analysis, IR and NMR (1H, 13C and 119Sn) spectra. The crystal structures of complexes 1,3 were determined by X-ray single crystal diffraction and showed that the tin atoms are in a distorted trigonal bipyramidal geometry and form five- and six-membered chelate rings with the tridentate ligand. Intermolecular weak interactions in 1,3 link molecules, respectively, into a two-dimensional array, a one-dimensional infinite chain and a one-dimensional double-chain supramolecular structure. Bioassay results of the compounds indicated that the dibutyltin complexes 3 and 4 have potent in vitro cytotoxic activity against two human tumor cell lines, CoLo205 and Bcap37, while the diethyltin complexes 1 and 2 display weak cytotoxic activity. Copyright © 2008 John Wiley & Sons, Ltd. [source] Imaging of quantum array structures with coherent and partially coherent diffractionJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2003I. A. Vartanyants Recent achievements in experimental and computational methods open the possibility of measuring and inverting the diffraction pattern from a finite object of submicrometer size. In this paper the possibilities of such experiments for two-dimensional arrays of quantum dots are discussed. The diffraction pattern corresponding to coherent and partial coherent illumination of a sample was generated. Test calculations based on the iterative algorithms were applied to reconstruct the shape of the individual islands in such a quantum structure directly from its diffraction pattern. It is demonstrated that, in the case of coherent illumination, the correct shape and orientation of an individual island can be obtained. In the case of partially coherent illumination, the correct shape of the particle can be obtained only when the coherence of the incoming beam is reduced to match the size of the island. [source] Single crystalline 2D porous arrays obtained by self organization in n-InPPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003S. Langa Abstract Self organization is a rather common phenomenon during pore formation in III,V semiconductors. The so called tetrahedron-like pores, the domains of crystallographically oriented pores in n-GaAs, or the macroscopic voltage oscillations in n-InP at high constant current densities are examples of a self organization process. In this paper we will discuss two-dimensional arrays of pores in n-InP with the unique property that they may form a single crystal as a result of a self organization process. The reasons for this long range order and its dependence on the etching conditions will be discussed. [source] Hopping magnetoresistance in two-dimensional arrays of Ge/Si quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2006A. I. Yakimov Abstract The temperature and magnetic field dependences of the conductivity associated with hopping transport of holes over 2D arrays of Ge/Si quantum dots with various filling factors are studied experimentally. A transition from the Efros-Shklovskii law for the temperature dependence of hopping conductivity to the Arrhenius law with an activation energy equal to 1.0-1.2 meV is observed upon a decrease in temperature. The activation energy for the low-temperature conductivity increases with the magnetic field and attains saturation in fields exceeding 4 T. It is found that the magnetoresistance in layers of quantum dots is essentially anisotropic: the conductivity decreases in magnetic fields oriented perpendicular to a dot layer and increases in a field whose vector lies in the plane of the sample. The absolute values of magnetoresistance for transverse and longitudinal field orientations differ by two orders of magnitude. Effect of spin correlations on the hopping magnetoresistance is discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Calcium(II) meso -2,3-diphenylsuccinate heptahydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2000Gregory Morin The title compound, [Ca(C16H12O4)(H2O)6]·H2O, adopts a conformation about the central C,C bond that places the two carboxylate groups in an anti orientation. The crystal consists of layers of two-dimensional arrays of 2,3-diphenylsuccinate dianions which are linked by bridging Ca2+ cations. The unit cell contains two Ca2+ cations in an unusual four-membered Ca,O,Ca,O ring in which the bridging O atoms belong to water molecules rather than carboxylates, i.e. poly[[[di-,-aqua-bis[pentaaquacalcium(II)]]-,-(meso -2,3-diphenylsuccinato- O:O,)] succinate dihydrate]. [source] | ||||||||||||||||