1,721,113 research outputs found
Free clusters in a supersonic beam probed by multicoincidence technique after core-level photoionization
No full textParameterization of a two-stage mass spectrometer performing second-order space focusing
No full textHigh mass resolution can be achieved with a time-of-flight mass spectrometer performing first-order space focusing in combination with supersonic molecular beams. The introduction of a second-order correction of the space focus allows an enhancement of the resolution. We present a general parameterization for designing a two-stage mass spectrometer performing second-order space focusing. This formalism is well suited for the design of instruments devoted to the study of clusters in molecular beams. Numerical simulations of the performance are presented
Manipulation of nanoparticles in supersonic beams for the production of nanostructured materials
No full textProduction and manipulation of nanoparticles in the gas phase is of primary importance for the synthesis of nanostructured materials and for the development of industrial processes based on nanotechnology. In this review we will present and discuss the approach based on the use of aerodynamic focusing methods coupled to supersonic expansions to obtain high intensity cluster beams with a control on nanoparticle mass and spatial distribution. The implication of this techniques for the synthesis of nanostructured materials will be also presented
Time-of-flight analysis of neutral cluster beams through detection of charged particles produced by cluster impact on a channeltron
No full textElectrical conduction in nanostructured carbon films produced by supersonic cluster beam deposition
No full textWe present a study on electrical conduction in nanostructured carbon films produced by deposition of a supersonic beam of neutral carbon clusters. The electrical transport properties have been investigated by measuring the electrical conductance both in-situ, during the film deposition, and ex-situ, after the film exposure to ambient air. The I-V characteristic indicates a strict ohmic behavior all over the measured electric field range up to (2 kV/cm). Changes in the electrical conductance have been observed due to gas adsorption-desorption mechanisms. The exposure to air leads to a passivation of the film with an increase of resistivity up to ∼ 0.1 GΩ.cm. Current-temperature characteristics measured in vacuum in the temperature range 150-400 K, both in-situ and ex-situ, indicate a thermally activated conductivity with energy of ∼ 0.3 eV
Electrochemical impedance spectroscopy on nanostructured carbon electrodes grown by supersonic cluster beam deposition
No full textNanostructured porous films of carbon with density of about 0.5 g/cm3 and 200 nm thickness were deposited at room temperature by supersonic cluster beam deposition (SCBD) from carbon clusters formed in the gas phase. Carbon film surface topography, determined by atomic force microscopy, reveals a surface roughness of 16 nm and a granular morphology arising from the low kinetic energy ballistic deposition regime. The material is characterized by a highly disordered carbon structure with predominant sp2 hybridization as evidenced by Raman spectroscopy. The interface properties of nanostructured carbon electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy employing KOH 1 M solution as aqueous electrolyte. An increase of the double layer capacitance is observed when the electrodes are heat treated in air or when a nanostructured nickel layer deposited by SCBD on top of a sputter deposited film of the same metal is employed as a current collector instead of a plain metallic film. This enhancement is consistent with an improved charge injection in the active material and is ascribed to the modification of the electrical contact at the interface between the carbon and the metal current collector. Specific capacitance values up to 120 F/g have been measured for the electrodes with nanostructured metal/carbon interface
Interfacial properties of a carbyne-rich nanostructured carbon thin film in ionic liquid
No full textNanostructured carbon sp2 (ns-C) thin films with up to 30% of sp-coordinated atoms (carbynes) were produced in a high vacuum by the low kinetic energy deposition of carbon clusters produced in the gas phase and accelerated by a supersonic expansion. Immediately after deposition the ns-C films were immersed in situ in an ionic liquid electrolyte. The interfacial properties of ns-C films in the ionic liquid electrolyte were characterized by electrochemical impedance spectroscopy and cyclic voltammetry (CV). The so-prepared carbyne-rich electrodes showed superior electric double layer (EDL) capacitance and electric conductivity compared to ns-C electrodes containing only sp2 carbon, showing the substantial influence of carbynes on the electrochemical properties of nanostructured carbon electrodes
Simulation on the effect of Brownian motion on nanoparticle trajectories in a pulsed microplasma cluster source
No full textWe describe a simulation of the nanoparticle trajectories in a pulsed cluster beam source. Clusters, formed by condensation of atomic vapor in a helium bath, and considered here as rigid spheres having a diameter of 1.5 nm, were tracked during their travel inside the source cavity, an aerodynamic lens, and a cylindrical nozzle. Steady state supersonic laminar flow of helium is considered in an axi-symmetric geometry aiming to simulate, within some limitations, the conditions under which cluster formation takes place in a pulsed microplasma cluster source. In spite of the unsteady nature of the pulsed source, the time scale characterizing particle motion in the flow field is significantly smaller than the characteristic time constant for the evolution of gas pressure in the source. For this reason, a steady simulation can shed some light on the understanding of processes governing nanoparticle motion in a pulsed vaporization source. The extent to which the Brownian diffusion can affect the particle extraction from the source is investigated. Simulations have shown that the Brownian motion perturbs the clusters from the trajectories dictated by the carrier gas and increases the rate of cluster deposition on the source internal walls. However, it does not hinder the aerodynamic focalization produced by the lens even in nano-size cluster regime. This result is qualitatively confirmed by experiment
Cluster beam microfabrication of patterns of three-dimensional nanostructured objects
No full textThis letter describes the use of supersonic cluster beam deposition (SCBD) through a stencil mask for the fabrication of patterns of cluster-assembled objects. Using carbon cluster beams, micrometer-size pillars and tips have been produced on a variety of substrates. SCBD is characterized by high deposition rates, high lateral resolution, and low temperature processing. Nanostructured objects can be produced with high aspect ratio and controlled shapes. Micropatterning with SCBD can be of interest for applications requiring the integration of cluster-assembled structures with microelectronic or micromechanical devices
Supersonic cluster beam deposition of nanostructured thin films with uniform thickness via continuously graded exposure control
No full textSupersonic cluster beam deposition is a powerful technique for the production of nanostructured thin films and the microfabrication with stencil masks of patterns with very good lateral resolution. The high focusing of cluster beam typical of supersonic expansions causes the deposition of films with strong thickness variation over a small area. To overcome this problem we have designed and tested a rotating screen allowing a continuously graded exposure of the substrate during cluster beam deposition. This allows the production of nanostructured films with uniform thickness over a large area while keeping all the features typical of supersonic beams
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