85 research outputs found

    A Three Dimensional Analysis of Au-Silica Core-Shell Nanoparticles Using Medium Energy Ion Scattering

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    The medium energy ion scattering (MEIS) facility at the IIAA Huddersfield has been used for the analysis of a monolayer of Au-silica core-shell nanoparticles deposited on Si substrate. Both spherical and rod shape particles were investigated and the spectra produced by 100 keV He+ ions scattered through angles of 90º and 125º were compared with the results of RBS-MAST [1] simulations performed on artificial 3D model cells containing the nanoparticles. The thickness of the silica shell, the diameter of the Au spheres, and the diameter and length of the Au nano-rods were determined from best fits of the measured set of MEIS spectra. In addition, the effect of ion irradiation on the silica shell and gold core was monitored by MEIS measurements in conjunction with RBS-MAST simulations. Ion bombardment was performed under largely different conditions, i.e., by 30 keV Ar+, 150 keV Fe+, or 2.8 MeV N+ ions in the dose range of 2×1015 - 2×1016 cm-2. Significant changes in the particle geometry can be observed due to ion beam-induced sputtering and recoil effects, the significance of which was estimated from full-cascade SRIM simulations. Rutherford backscattering spectrometry (RBS), Field emission scanning electron microscopy (FESEM), and Atomic Force Microscopy (AFM) techniques have been applied as complementary characterization tools to monitor the amount of gold and surface morphology on the un-irradiated and irradiated sample areas. We show that MEIS can yield spatial information on the geometrical changes of particulate systems at the nanometre scale

    Antibacterial properties of Ag-TiO2 composite sol-gel coatings

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    This study reveals the connection between the silver-doping method, the resulting nature and amount of the silver dopant together with the structural properties and the long-term antibacterial activity of composite coatings.</p

    Schottky Barrier Modulation of Metal/4H-SiC Junction with Thin Interface Spacer Driven by Surface Polarization Charge on 4H-SiC Substrate

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    The Au/Ni/Al2O3/4H-SiC junction with the Al2O3 film as a thin spacer layer was found to show the electrical characteristics of a typical rectifying Schottky contact, which is considered to be due to the leakiness of the spacer layer. The Schottky barrier of the junction was measured to be higher than an Au/Ni/4H-SiC junction with no spacer layer. It is believed that the negative surface bound charge originating from the spontaneous polarization of 4H-SiC causes the Schottky barrier increase. The use of a thin spacer layer can be an efficient experimental method to modulate Schottky barriers of metal/4H-SiC junctions.open

    Single - and double energy swift and slow heavy ion irradiated optical waveguides in Er: Tungstene-Tellurite glass and BGO for telecom applications

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    The fabrication of broadband amplifiers in wavelength division multiplexing (WDM) around 1.55 m, as they exhibit large stimulated cross sections and broad emission bandwidth. Bi4Ge3O12 (eultine type BGO) - well known scintillator material, also a rare-earth host material, photorefractive waveguides produced in it only using light ions in the past. Recently: MeV N+ ions and swift O5+ and C5+ ions, too*. Bi12GeO20 (sillenite type BGO) - high photoconductivity and photorefractive sensitivity in the visible and NIR good candidate for real-time holography and optical phase conjugation, photorefractive waveguides produced in it only using light ions. No previous attempts of ion beam fabrication of waveguides in it

    Optical and structural characterization of Ge clusters embedded in ZrO2

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    The change of optical and structural properties of Ge nanoclusters in ZrO2 matrix have been investigated by spectroscopic ellipsometry versus annealing temperatures. Radio-frequency top-down magnetron sputtering approach was used to produce the samples of different types, i.e. single-layers of pure Ge, pure ZrO2 and Ge-rich-ZrO2 as well as multi-layers stacked of 40 periods of 5-nm-Ge-rich-ZrO2 layers alternated by 5-nm-ZrO2 ones. Germanium nanoclusters in ZrO2 host were formed by rapid-thermal annealing at 600-800 ∘C during 30 s in nitrogen atmosphere. Reference optical properties for pure ZrO2 and pure Ge have been extracted using single-layer samples. As-deposited multi-layer structures can be perfectly modeled using the effective medium theory. However, annealed multi-layers demonstrated a significant diffusion of elements that was confirmed by medium energy ion scattering measurements. This fact prevents fitting of such annealed structure either by homogeneous or by periodic multi-layer model

    M-line spectroscopic, spectroscopic ellipsometric and microscopic measurements of optical waveguides fabricated by MeV-energy N+ ion irradiation for telecom applications

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    Irradiation with N+ ions of the 1.5 - 3.5 MeV energy range was applied to optical waveguide formation. Planar and channel waveguides have been fabricated in an Er-doped tungsten-tellurite glass, and in both types of bismuth germanate (BGO) crystals: Bi4Ge3O12 (eulytine) and Bi12GeO20 (sillenite). Multi-wavelength m-line spectroscopy and spectroscopic ellipsometry were used for the characterisation of the ion beam irradiated waveguides. Planar waveguides fabricated in the Er-doped tungsten-tellurite glass using irradiation with N+ ions at 3.5 MeV worked even at the 1550 nm telecommunication wavelength. 3.5 MeV N+ ion irradiated planar waveguides in eulytine-type BGO worked up to 1550 nm and those in sillenite-type BGO worked up to 1330 nm
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