1,721,034 research outputs found
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
Cluster beam synthesis of nanostructured thin films
No full textThe use of clusters as elemental building blocks can open routes toward the fabrication of a new class of nanostructured solids and devices. We report the synthesis of nanostructured films using supersonic cluster beam deposition. A new type of cluster source based on microplasma ablation has been developed. This allows a substantial improvement in terms of deposition rate and control on cluster mass distribution. These achievements make supersonic cluster beams a useful tool in the arena of cluster assembling of materials. We have applied this technique to the growth of nanostructured carbon thin films. The structure and morphology of the films can be controlled by varying the cluster mass distribution prior to deposition. Deposition conditions affect the surface roughness and the onset of scale-invariant morphology on a dimension domain extending from the nanometer up to the micrometer. The cluster beam deposition method shows very promising features in view of the large scale growth of nanostructured films with novel functional and structural properties. The patterning of three-dimensional nanostructured objects is also demonstrated
Electrical 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
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
A comparative study between AFM and SEM imaging on human scalp hair
No full textA comparative study of AFM and SEM imaging of the same area of a human scalp hair has been carried out to determine the similarity and the differences between the two techniques. Sample preparation for SEM analysis requires a metallization step and vacuum exposure, both of which could potentially induce modifications to the surface details. By contrast, AFM is a suitable technique to evaluate any effect resulting from sample manipulation because it can be applied without any specific treatment. AFM analysis demonstrates that sample metallization is responsible for modifications to the surface details of hair, mainly comprising an increase in height of scale steps and of root mean square roughness together with variation in scale profiles. Sample treatments for SEM imaging are in general potentially responsible for surface modifications to the samples involved
Sistema a maschera rigida auto-allineante per la produzione di massa di dispositivi a base silicio funzionalizzati mediante fasci di nano-particelle
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A novel MEMS-based multiparameter sensor
No full textMEMS technology has emerged more than two decades ago and, since then, it has evolved rapidly and steadily, realizing various types of physical sensors and actuators. Micro-fabrication techniques have also been developed for the realization of micro-platforms for chemiresistive gas sensors. In recent years, many examples of this class of devices have appeared in literature, the typical implementation being suspended microstructures in a cavity of silicon for thermal insulation, on which sensing material are coated. The major benefit of these microplatforms is the drastic reduction of power consumption, which allows the gas sensor to be battery-driven. Together with the extreme miniaturization of these devices, this can lead to wireless or portable gas sensors, and to ubiquitous sensor systems. However, there is a major problem to overcome, which hinders the commercialization of these innovative micro gas sensors. The challenge is to develop robust microfabrication techniques to deposit well-quantified sensing layer efficiently on a microplatforms, without affecting the yield of the microfabrication process. Recently, our group has implemented into the MEMS-based process for micro gas sensor, the technology to deposit nanostructured metal oxides on microplatforms by supersonic cluster beam deposition (SCBD), which represents a feasible solution to this problem. This technology is, in fact, very easy to integrate inside a microfabrication process and lead us to development of a novel multiparameter MEMS-based device.
This paper reports the design, realization and characterization of a novel MEMS-based multiparameter sensor, which integrates on the same silicon chip a calorimetric flow sensor, a nanostructured metal-oxide gas sensor and a gas temperature sensor. Potential applications are in the field of environmental and air quality monitoring, control of industrial processes, detection of harmful emissions and chemical warfare and medical diagnostics
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