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End date: 2019 × Start date: 2019 × DDC: 540 × Type: Text × Publisher: Bristol : IOP Publishing ×

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    Fabrication of metal nanoparticle arrays by controlled decomposition of polymer particles
    (Bristol : IOP Publishing, 2013) Brodoceanu, Daniel; Fang, Cheng; Voelcker, Nicolas Hans; Bauer, Christina T.; Wonn, Anne; Kroner, Elmar; Arzt, Eduard; Kraus, Tobias
    We report a novel fabrication method for ordered arrays of metal nanoparticles that exploits the uniform arrangement of polymer beads deposited as close-packed monolayers. In contrast to colloidal lithography that applies particles as masks, we used thermal decomposition of the metal-covered particles to precisely define metal structures. Large arrays of noble metal (Au, Ag, Pt) nanoparticles were produced in a three-step process on silicon, fused silica and sapphire substrates, demonstrating the generality of this approach. Polystyrene spheres with diameters ranging between 110 nm and 1 µm were convectively assembled into crystalline monolayers, coated with metal and annealed in a resistive furnace or using an ethanol flame. The thermal decomposition of the polymer microspheres converted the metal layer into particles arranged in hexagonal arrays that preserved the order of the original monolayer. Both the particle size and the interparticle distance were adjusted via the thickness of the metal coating and the sphere diameter, respectively.
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    Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching
    (Bristol : IOP Publishing, 2016) Brodoceanu, Daniel; Alhmoud, Hashim Z.; Elnathan, Roey; Delalat, Bahman; Voelcker, Nicolas H.; Kraus, Tobias
    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.