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Magnetic Properties of 100 NM-Period Nickel Nanowire Arrays Obtained from Ordered Porous-Alumina Templates. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-636-d1.9.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractNi nanowires were grown in highly-ordered anodic alumina templates using pulsed electrodeposition. This technique yields completely metal-filled alumina membranes. The magnetic behavior of 100 nm period arrays of Ni nanowires with a length of 1 μ and different diameters has been characterized using SQUID magnetometry and magnetic force microscopy. Reducing the diameter from initially 50 to 25 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 Oe to 1200 Oe and to increasing remanence from 30% to 100% of the hysteresis. The deposition of Ni65Fe35 gave a further improvement of the coercive fields up to 1350 Oe.
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Abstract
ABSTRACTRecently we presented a formation mechanism for micro-porous silicon which is based on a depletion of holes in the porous region due to quantum confinement. This theory allows predictions concerning the dependence of the porous morphology on the formation conditions. It is the purpose of this work to check whether these predictions are in accordance with experimental observations.
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Abstract
ABSTRACTAn overview of the behavior of intrinsic point defects in silicon and their interaction with carbon is given for temperatures above about 500° C. The diffusive mechanism of carbon in silicon, which involves silicon self-interstitials, is treated in some detail and compared with the diffusion mechanism of oxygen. The solubility of interstitial carbon is estimated. Co-precipitation of carbon and self-interstitials or oxygen are dealt with in terms of simple volume considerations. It is proposed that the contradicting results on the influence of intrinsic point defect supersaturations on oxygen nucleation and precipitation may possibly be explained in the frame-work of opposite effects depending on the carbon concentration. Finally the influence of carbon on the incorporation and diffusion of gold in silicon is discussed.
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Abstract
ABSTRACTIn a first part, we deal with the influence of intrinsic point defects (vacancies and self-interstitials) on self- and impurity diffusion in silicon. Estimates of the diffusivities and thermal equilibrium concentrations of vacancies and self-interstitials are given. In a second partwe discuss the influence of point defects on the diffusion and precipitation of different types of metallic impurities in various gettering schemes as well as on the nucleation and growth of SiO2 precipitates.
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Abstract
AbstractA perfect 2D porous alumina photonic crystal with 500 nm interpore distance was fabricated on an area of 4 cm2 via imprint methods and subsequent electrochemical anodization. A 4” imprint stamp consisting of a convex pyramid array was obtained by modern VLSI processing using DUV-lithography, anisotropic etching, LPCVD Si3N4 deposition and wafer bonding. The optical properties of the porous alumina photonic crystal were measured with an infrared microscope in Г-M direction. For both polarizations, a bandgap is observed at around 1 μm for r/a = 0.42. A reflectivity of almost unity for E-polarization in the region of the bandgap is a sign of the high quality of the structure, indicating almost no scattering losses. These experimental results could be correlated very well to the bandstructure as well as reflectivity calculations assuming a dielectric constant of å = 2.0 for the anodized alumina.
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Synthesis and structural characterisation of Si and SiOx particles of nanometer sizes. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19971011117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Nanoscale patterning induced strain redistribution in ultrathin strained Si layers on oxide. NANOTECHNOLOGY 2010; 21:134013. [PMID: 20208119 DOI: 10.1088/0957-4484/21/13/134013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present a comparative study of the influence of the thickness on the strain behavior upon nanoscale patterning of ultrathin strained Si layers directly on oxide. The strained layers were grown on a SiGe virtual substrate and transferred onto a SiO(2)/Si substrate using wafer bonding and hydrogen ion induced exfoliation. The post-patterning strain was evaluated using UV micro-Raman spectroscopy for thin (20 nm) and thick (60 nm) nanostructures with lateral dimensions in the range of 80-400 nm. We found that about 40-50% of the initial strain is maintained in the 20 nm thick nanostructures, whereas this fraction drops significantly to approximately 2-20% for the 60 nm thick ones. This phenomenon of free surface induced relaxation is described using detailed three-dimensional finite element simulations. The simulated strain 3D maps confirm the limited relaxation in thin nanostructures. This result has direct implications for the fabrication and manipulation of strained Si nanodevices.
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Silicon nanowire oxidation: the influence of sidewall structure and gold distribution. NANOTECHNOLOGY 2009; 20:405607. [PMID: 19738306 DOI: 10.1088/0957-4484/20/40/405607] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The oxidation behavior of Si nanowires (SiNWs) grown by the gold (Au) catalyzed vapor-liquid-solid (VLS) growth process in an electron beam evaporation (EBE) reactor is studied. The VLS SiNWs exhibit hexagonal shape with essentially {112} facets where each facet shows a saw-tooth faceting itself, consisting of alternating {111} and {113} facets. Depending on growth temperatures (450-750 degrees C) and evaporation currents (40-80 mA) that determine the silicon vapor supply, this facet formation is more or less pronounced. The diffusion of Au atoms on the faceted SiNW surfaces and the formation of Au nanoparticles on the SiNW facets during growth and during ex situ annealing are studied. Upon diffusion, the Au atoms agglomerate and form Au nanoparticles that preferably arrange themselves on {113} facets. Upon annealing in air at temperatures between 800 and 950 degrees C the gold nanoparticles agglomerate further and form bigger particles of a few tens of nm in diameter that reside at the interface between the growing silica (SiO(2)) layer and the SiNW itself, which in turn shrinks during SiNW oxidation. The oxide layer thickness and the oxide appearance depend on the annealing conditions (time and temperature) and systematically varied oxidation processing is described in this paper as investigated by cross-sectional transmission electron microscopy (TEM) including high resolution studies as well as scanning electron microscopy (SEM) studies. Our results strongly suggest that the SiNWs can be fully oxidized, thus forming silica NWs that can either keep their initial shape or, under certain annealing conditions, do not keep their initial wire shape but assume a bamboo-like shape that forms most likely as a result of locally high stresses that are related to nanocrack formation. The nanocracks form in the growing oxide layer mediated by the presence of Au nanoparticles that yield gold-enhanced SiNW oxidation and thus a faster oxidation rate.
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Oxide layer dissolution in Si/SiOx/Si wafer bonded structures. CRYSTAL RESEARCH AND TECHNOLOGY 2009. [DOI: 10.1002/crat.200900467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Selectively Deposited Silver Coatings on Gold-Capped Silicon Nanowires for Surface-Enhanced Raman Spectroscopy. Chemphyschem 2009; 10:1219-24. [DOI: 10.1002/cphc.200800809] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Fluorescence signals of core-shell quantum dots enhanced by single crystalline gold caps on silicon nanowires. NANOTECHNOLOGY 2009; 20:165301. [PMID: 19420566 DOI: 10.1088/0957-4484/20/16/165301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We use nanoscale (20-300 nm in diameter) single crystalline gold (Au)-caps on silicon nanowires (NWs) grown by the vapor-liquid-solid (VLS) growth mechanism to enhance the fluorescence photoluminescence (PL) signals of highly dilute core/shell CdSeTe/ZnS quantum dots (QDs) in aqueous solution (10(-5) M). For NWs without Au-caps, as they appear, for example, after Au etching in aqua regia or buffered KI/I(2)-solution, essentially no fluorescence signal of the same diluted QDs could be observed. Fluorescence PL signals were measured using excitation with a laser wavelength of 633 nm. The signal enhancement by single crystalline, nanoscale Au-caps is discussed and interpreted based on finite element modeling (FEM).
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Herstellung von Nanostrukturen mittels Atomlagenabscheidung. CHEM-ING-TECH 2008. [DOI: 10.1002/cite.200800107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane. NANOTECHNOLOGY 2008; 19:335604. [PMID: 21730626 DOI: 10.1088/0957-4484/19/33/335604] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.
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A model of extrusions and intrusions in fatigued metals I. Point-defect production and the growth of extrusions. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/01418618108239541] [Citation(s) in RCA: 330] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices. NANOSCALE RESEARCH LETTERS 2006; 1:137. [PMCID: PMC3246673 DOI: 10.1007/s11671-006-9004-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The luminescence properties of highly strained, Sb-doped Ge/Si multi-layer heterostructures with incorporated Ge quantum dots (QDs) are studied. Calculations of the electronic band structure and luminescence measurements prove the existence of an electron miniband within the columns of the QDs. Miniband formation results in a conversion of the indirect to a quasi-direct excitons takes place. The optical transitions between electron states within the miniband and hole states within QDs are responsible for an intense luminescence in the 1.4–1.8 µm range, which is maintained up to room temperature. At 300 K, a light emitting diode based on such Ge/Si QD superlattices demonstrates an external quantum efficiency of 0.04% at a wavelength of 1.55 µm.
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Highly directional emission from photonic crystal waveguides of subwavelength width. PHYSICAL REVIEW LETTERS 2004; 92:113903. [PMID: 15089137 DOI: 10.1103/physrevlett.92.113903] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Indexed: 05/24/2023]
Abstract
Recently it has been shown that it is possible to achieve directional emission out of a subwavelength aperture in a periodically corrugated metallic thin film. We report on theoretical and experimental studies of a related phenomenon concerning light emitted from photonic crystal waveguides that are less than a wavelength wide. We find that the termination of the photonic crystal end facets and an appropriate choice of the wavelength are instrumental in achieving very low numerical apertures. Our results hold promise for the combination of photonic crystal waveguides with conventional optical systems such as fibers, waveguides, and freely propagating light beams.
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Spin-wave quantization in ferromagnetic nickel nanowires. PHYSICAL REVIEW LETTERS 2002; 89:027201. [PMID: 12097013 DOI: 10.1103/physrevlett.89.027201] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Indexed: 05/23/2023]
Abstract
The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires. The results show that it is important to take proper account of these effects for the fundamental physics and future technological developments of magnetic nanowires.
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A model system for two-dimensional and three-dimensional photonic crystals: macroporous silicon. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/1464-4258/3/6/362] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Single-mode transmission in two-dimensional macroporous silicon photonic crystal waveguides. OPTICS LETTERS 2000; 25:1550-1552. [PMID: 18066275 DOI: 10.1364/ol.25.001550] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report the infrared operation of a two-dimensional photonic crystal waveguide fabricated in silicon. Measurements of the transmission spectrum reveal a large transmission bandwidth within the 3.1-5.5-microm bulk-crystal photonic bandgap and a rich resonance structure. The calculated transmission spectrum for this structure is in good agreement with the measured spectrum and predicts a 10% single-mode bandwidth for the waveguide.
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Modification of Si(100)-Surfaces by SF6 Plasma Etching — Application to Wafer Direct Bonding. CRYSTAL RESEARCH AND TECHNOLOGY 2000. [DOI: 10.1002/1521-4079(200007)35:6/7<807::aid-crat807>3.0.co;2-j] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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A fuzzy logic approach to HREM image analysis of III–V compounds. Inf Sci (N Y) 1996. [DOI: 10.1016/0020-0255(96)00088-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Direct formation of vertically coupled quantum dots in Stranski-Krastanow growth. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:8743-8750. [PMID: 9984553 DOI: 10.1103/physrevb.54.8743] [Citation(s) in RCA: 179] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Ultranarrow Luminescence Lines from Single Quantum Dots. PHYSICAL REVIEW LETTERS 1995; 74:4043-4046. [PMID: 10058398 DOI: 10.1103/physrevlett.74.4043] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Structural characterization of (In,Ga)As quantum dots in a GaAs matrix. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:14766-14769. [PMID: 9978423 DOI: 10.1103/physrevb.51.14766] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Metastability in slow thin-film reactions. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:1198-1201. [PMID: 9996323 DOI: 10.1103/physrevb.43.1198] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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A new approach to the statistics of nuclear spin-lattice relaxation caused by paramagnetic impurities. ACTA ACUST UNITED AC 1976. [DOI: 10.1016/0378-4363(76)90028-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Anisotropic diffusion, long-range energy transfer and bimolecular exciton recombination kinetics. Chem Phys Lett 1976. [DOI: 10.1016/0009-2614(76)80756-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Extension of Förster's Theory of Long-Range Energy Transfer to Donor-Acceptor Pairs in Systems of Molecular Dimensions. ACTA ACUST UNITED AC 1976. [DOI: 10.1524/zpch.1976.101.1-6.255] [Citation(s) in RCA: 73] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Eine neue, ausbaufähige Theorie der Statistik der weitreichenden Dipol-Dipol-Energieübertragung nach Förster. Z PHYS CHEM 1976. [DOI: 10.1524/zpch.1976.99.1-3.081] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Recovery kinetics in stages IDand IEof irradiated metals—one-dimensional versus three-dimensional interstitial migration. ACTA ACUST UNITED AC 1975. [DOI: 10.1080/00337577508237423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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