Highly stable Ag nanoparticles in agar-agar matrix as inorganic-organic hybrid

cited By 15International audienceA novel synthesis of inorganic-organic hybrid films containing well dispersed and almost uniform size Ag nanoparticles in agar-agar matrix has been reported. The films are found to be highly stable for more than a year. The colloidal particles of Ag can be obtained in large quantities in the form of a film or in the gel form when dispersed in agar-agar or by dissolving in a suitable solvent as solution. Characterization has been done by UV-visible spectroscopy and TEM. The hybrid may be of interest to study third-order non-linear susceptibility

In-Situ Electrical Biasing of Electrically Connected TEM Lamellae with Embedded Nanodevices

International audienceIn response to a continually rising demand for high performance and low-cost devices, and equally driven by competitivity, the microelectronics industry excels in meeting innovation challenges and further miniaturizing products. However, device shrinkage and the increasing complexity of device architecture require local quantitative studies. In this paper, we demonstrate with a case study on a nanocapacitor, the capability of transmission electron microscopy in electron holography mode to be a unique in-situ technique for mapping electric fields and charge distributions on a single device

Aluminum metallization and wire bonding aging in power MOSFET modules

A limiting factor for the long-term reliability of power MOSFET-based devices is the electro-thermal and/or thermo-mechanical aging of the metallic parts. In this paper we assess the bonding wire and source metallization degradation of power devices, designed for applications in the automotive industry. Our approach consists in characterizing the metal microstructure before and after accelerated aging tests, by scanning electron microscopy, ion milling and microscopy, focused ion beam tomography, transmission electron microscopy and grain structure mapping. To focus on the wire-metallization bonding interface, we have set up a dedicated sample preparation that allows us to disclose the metallization under the bonding wires. This critical location is significantly different from the naked metallization, as the bonding process induces plastic deformation prior to aging. The main mechanism behind the device failure is the generation and propagation of fatigue cracks in the aluminum metallization. Away and under the wire bonds, they run perpendicularly from the surface down to the silicon substrate following the grain boundaries, due to an enhanced self-diffusion of aluminum atoms. Moreover, initial imperfections in the wire-metallization bonding (small cavities and aluminum oxide residues) are the starting point for harmful cracks that propagate along the wire-metallization interface and can eventually cause the wire lift-off. These phenomena can explain the local increase in the device resistance occurring at failure

Facile One-Pot Synthesis of White Emitting Gold Nanocluster solutions composed of Red, Green and Blue Emitters

International audienceGold nanoclusters (AuNC) have emerged as a new class of stable and biocompatible photo-emitters. While red emitting clusters comprising ca. 20-25 Au atoms are readily synthesized by several methods, smaller clusters with higher energy luminescence are much less commonly reported. Here, we report on a straightforward one-step synthesis of red, green, blue and violet emitting AuNC in mild conditions. Produced in pure ethylene glycol, the structural and optical properties of the AuNC are tuned by adding either aniline or indole. By combining high-resolution TEM, electrospray ionization mass spectrometry, X-ray photoelectron and photoluminescence spectroscopy, we identify Au6 (blue), Au11 (green) and Au22 (red) in solutions produced with aniline. This tricolor mixture produces a pure white luminescence under broadband excitation. The Au5 (violet) and Au7 (blue) produced with indole exhibit a large 27% quantum yield making them among the brightest blue emitting gold clusters. Importantly, when the AuNC are capped with a thiopegylated ligand shell bearing a terminal carboxylate, amine or biotin, they are made water soluble and stable while preserving intact their photo-physical characteristics. This work provides an easy access to robust emitters with tunable fluorescence and surface functionality for potential use in biolabelling, hyperspectral sensing or display technology

Confinement effects on the shape and composition of bimetallic nano-objects in carbon nanotubes

International audienceCoPt and FePt nanostructures have been efficiently confined in carbon nanotubes (CNTs). A marked confinement effect has been evidenced, both on bimetallic nano-object shape and composition. In large diameter CNTs small Co-and Fe-rich nanoparticles are formed, while in small diameter CNTs Pt-rich nanowires are selectively produced

Contribution of Primary γ′ Precipitates in the Deformation Creep Mechanisms in the Ni-Based Polycrystalline AD730TM Superalloy

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Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

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Electro-precipitation of Fe3O4 nanoparticles in ethanol

cited By 49International audienceThe preparation of superparamagnetic magnetite (Fe3O4) nanoparticles by electro-precipitation in ethanol is proposed. Particle average size can be set from 4.4 to 9 nm with a standard deviation around 20%. Combination of wide-angle X-ray scattering (WAXS), Electron energy loss spectroscopy (EELS) and Mössbauer spectroscopy characterizations clearly identifies the particles as magnetite single-crystals (Fe3O4)

Creep behavior in the new AD730TM nickel-based disk superalloy – Influence of aging heat treatment and local chemical fluctuations

International audienceTransmission electron microscopy (TEM) experiments combining conventional and weak beam observations, energy dispersive X-ray and electron energy loss spectroscopies have been used to identify and quantify, in the polycrystalline AD730TM Ni-Based superalloy, the effect of isothermal aging after solution treatment in the range 730--790 °C on the creep behavior at 700 °C -- 500 MPa. The microstructure of different aged crept specimens has been first characterized as the creep behavior is directly influenced by the microstructural features (size of the γ′ precipitates and of the γ-channel). The analyzes show similar results whatever the heat treatment. Then, the investigation of the dislocation configurations indicate that the deformation occurs by the propagation of straight perfect dislocations, which shear the γ-matrix and the precipitates at 730 °C and 760 °C, whereas a combination of perfect and partial dislocations is observed after aging at 790 °C. The investigation of the local chemical composition has revealed some strong local variations in Cr content within the γ-phase and smaller ones in Ti content within the γ′-phase after aging at 790 °C. These elemental concentration quantifications have been used to evaluate the antiphase boundary and stacking fault energies. This allows to interpret the presence of partial dislocations after aging at 790 °C and thus the increase in the creep strain rate when the specimen is previously aged at 790 °C

Self-organization and tunable characteristic lengths of two-dimensional hexagonal superlattices of nanowires directly grown on substrates

International audienceThe organization of nano-objects on macroscopic surfaces is a key challenge for the technological improvement and implementation of nanotechnologies. For achieving operational functions, it is required to assemble nano-objects as controllable building blocks in highly ordered superstructures. Here we demonstrate the growth and self-organization of metallic nanowires on surfaces into hexagonal superlattices with tunable characteristics lengths depending of the used stabilizing surfactants. Starting from a reacting mixture containing a Pt(111) substrate, a Co organo-metallic precursor, an amine and an acid dissolved in a solvent, we quantify the structural evolution of superlattices of vertical single-crystalline Co nanowires on Pt using a combined analysis of small angle neutron scattering, transmission and scanning electron microscopies. It is shown the concerted steps of growth and self-organization of the nanowires into a spontaneous 2D hexagonal lattice on Pt, at intervals starting from a few hours of reaction to a highly ordered superlattice at longer times. Furthermore, it is shown that apart from long-chain acid and long chain aliphatic amine pairs used as stabilizers, the combination of a long chain aliphatic and a short aromatic ligand in the synthesis can be also employed for the nanowire superlattices development. Interestingly the possibility to employ different pairs allows quantitative modulation of the nanowire arrays, such as the interwire distance and the packing fraction