196,451 research outputs found
L'uomo tecnologo e creatore
No full textA partire dalla riflessione sul legame esistente tra tecnologia e sviluppo umano, si discute della eticità della tecnologia specie quando opera in domini particolarmente rischiosi per l'esistenza dell'umanità (per esempio, l'energia nucleare). Si riconosce come oggi la tecnologia non possa più essere affrontata pensando l'uomo come una creatura, ma piuttosto come un creatore. Da qui l'importanza anche della riflessione teologica per una tecnologia che voglia costruire una sua eticità, per liberarsi dalla soggezione economica a favore di una sempre maggiore libertà culturale
Modulated RF discharges as effective tool for selecting excited species
No full textModulated NH3-fed rf glow discharges have been investigated; the emissions of the active species NH* and N-2* have been collected during the modulation period (time on+time off). In this study, modulated discharges have been characterized by a constant time on of 7 ms and a tunable time off in the range of 0-1000 ms. It has been found that the power modulation represents an effective tool for selecting excited species: this procedure may be exploited in surface grafting treatments of polymers where high selectivity of chemical groups is requested, e.g., for preferentially grafting -NH2 groups onto polyethylene with respect to all other N-containing functionalities
Process control for plasma processing of polymers
No full textPE-CVD processes of a variety of coatings - fluoropolymers, SiOx, PEO- and Ag-PEO-like, -COOH functional layers - are described, as well as plasma treatments aimed to selectively graft -NH2 groups on polymers, with the use of spectroscopic plasma- and surface-diagnostics parameters of potential use for process transfer and control in industrial applications
’SiOx structural modifications by ion bombardment and their influence on electrical properties
No full textThe effect of an Ar/O-2 plasma treatment with additional ion bombardment delivered towards silicon suboxides layers has been investigated in terms of induced surface modifications, i.e., morphology, chemistry and electrical properties. Atomic Force Microscopy witnesses the smoothening of the silicon suboxide surface, dependent on the developed bias voltage at the substrate and the treatment time. Spectroscopic ellipsometry points out the optical properties of the modified surface: a thin silicon dioxide layer (5-17 nm) develops as a consequence of the surface process densification, also found to be dependent on the bias voltage and treatment time. Electrical properties (in terms of electric conductivity and layer capacity) are also reported on both the as deposited and ion bombarded samples
NH3 plasma treatments of PET for enhancing Al adhesion
No full textANH3 plasma process has been studied for enhancing the adhesion of aluminum coatings
on polyethyleneterephtalate (PET) films. According to our peel strength results,
NH3 plasmas increase markedly the adhesion of aluminum on PET compared to O2 discharges,
with a much shorter treatment time. A tentative model of nonhindered growth
of Al-coating based on the Lewis basic character of the functionalities grafted by NH3
plasma is proposed for Al-polymer interactions, and for explaining the various steps
in the process. The effects of power input and treatment time on the polymer surface
chemistry and on the metal-polymer peel strength have been evaluated. Treatment times
as short as 0.1 s at 100Wproved to be the best conditions in NH3 plasmas, for a significant
increase in Al/PET adhesion, while longer treatments have a detrimental effect.
This may explain why most authors have not discovered the benefits of NH3 plasmas for
improving the adhesion of metals on PET, and have preferred O2 or air treatments. The
relative basicity of PET grafted with N-containing functionalities has been measured
by means of X-ray Photoelectron Spectroscopy (XPS) analysis of samples exposed to
vapors of trichloromethane, a Lewis acid molecular probe. The Al/PET adhesion was
evaluated by means of a 180± Peel Test
Quantum Theory of Spontaneous Emission in Multilayer Dielectric Structures
No full textThis paper is a theoretical one dealing with spontaneous emission in one-dimensional photonic structures.
We present a fully quantum-electrodynamical formalism suitable to evaluate the spontaneous emission rate and pattern from a dipole embedded in a nonabsorbing and lossless multilayer dielectric structure. In the model here developed the electromagnetic field is quantized by a proper choice of a complete and orthonormal set of classical spatial modes, which consists of guided and radiative (partially and fully) states. In particular, by choosing a set of radiative states characterized by a single outgoing component, we get rid of the problem related to the quantum interference between different outgoing modes, which arises when the standard radiative basis is used to calculate spontaneous emission patterns. After the derivation of the local density of states, the analytical expressions for the emission rates are obtained within the framework of perturbation theory. First we apply our model to realistic silicon-based structures such as a single Si/air interface and a silicon waveguide in both the symmetric and asymmetric configurations. Then, we focus on the analysis of the spontaneous emission process in a silicon-on-insulator (SOI) slot waveguide (a six-layer model structure) doped with Er3+ ions. In this latter case we find a very good agreement with the experimental evidence [M. Galli et al., Appl. Phys. Lett. 89, 241114 (2006)] of an enhanced TM/TE photoluminescence signal. Hence, this model is relevant to study the spontaneous emission in silicon-based multilayer structures which nowadays play a fundamental role for the development of highly integrated multifunctional devices
Evolution of surface morphology of SiO2-like films deposited by means of the Expanding Thermal Plasma
No full textRemote Plasma Deposited Silicon Dioxide-Like Film Densification by Means of RF Substrate Biasing: Film Chemistry and Morphology
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