Results 1 - 10 of 19948
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[en] When reducing the size of array elements and interelement separations to the nanoscale, long-range magnetostatic interactions become important. A methodology that extends the study of conventional single-element magnetostatics is presented, adding the effect of stacking nanoelements into close proximity in arrays and the consequent interaction effects. This would be very time consuming to model by micromagnetic simulations that are also very vulnerable to artifacts due to cell or boundary condition selection. The proposed method considers an analytical expression valid for short interelement separations and not very costly to evaluate by computational means. This approach allows the quantitative study of shape anisotropy in non-square-shaped arrays. It is also shown how it can be used to find anisotropy compensation conditions, where an anisotropy due to a magnetic element shape can be compensated by the shape anisotropy due to the array. The obtained results can be used to establish a criterion for the minimum number of elements to be considered for a micromagnetic simulation of an array to be realistic depending on the element size and separation
[en] Results of nonlinear simulations of convective flows in two-layer systems on different scales under the action of a temperature gradient along the interface, are presented. Both purely thermocapillary flows and buoyant-thermocapillary flows are considered. Also, the nonlinear development of the instability in ultra-thin films caused by intermolecular forces, is investigated
[en] The relaxation dynamics of Preisach superpositions of thermally activated, bistable elements are shown to exhibit aging and memory effects in response to certain field- and temperature-cycling protocols, which are reminiscent of those observed in spin glasses, but which are not a consequence of collective freezing. Model simulations are able to replicate memory effects observed in a thin film of Fe nanoparticles embedded in glass
[en] Ti–Ni–Cu shape memory thin films within a broad composition range were investigated by the cantilever deflection method using combinatorial methods. Optimal compositions with improved functional properties, i.e. large recovery stress, high transformation temperatures, low thermal hysteresis width and small temperature interval of transformation, were identified using a newly defined figure of merit. Of the investigated alloys, Ti50Ni41Cu9 and Ti45Ni46Cu9 exhibit the best shape memory properties for compositions showing a B2→B19 and a B2→R-phase transformation, respectively
[en] Electron Irradiation can be applied towards nano-floating gate memories which are recognized as one of the next-generation nonvolatile memory semiconductors. NFGMs can overcome the preexisting limitations encountered in Dynamic Random Access Memories and Flash memories with the excellent advantages, i. e. high-density information storage, high response speed, high compactness, etc. The traditional nano-floating gate memories are fabricated through multi-layered nano structures of the dissimilar materials where the charge-trapping portions are sandwiched into the high-k dielectrics. However, this work reports the unique nonvolatile responses in single-layered high-k dielectric thin films if irradiated with highly accelerated electron beams. The implications of the electron irradiation will be discussed towards high-performance nano-floating gate memories
[en] Current density–voltage (J–V) characteristics of regioregular poly(3-hexylthiophene) (P3HT) thin-film sandwiched structures are studied and analyzed in this paper. Various material and trap parameters are estimated using the space-charge-limited conduction model with exponential trap distribution. Temperature-dependent J–V characteristics are examined to justify the bulk-limited transport in the material and trap density (Hβ) and characteristic constant (Et) are determined. The model is modified using field-dependent trap occupancy (FDTO) and compared. Both the models, with and without FDTO, fit the J–V curves at different temperatures. Though the model with FDTO fits the J–V curve slightly better at high voltages when compared to the model without FDTO, it cannot be established with certainty
[en] We develop a model based on Fick's law of diffusion as a phenomenological description of the molecular motion, and on the coupled mode theory, to describe single-beam surface relief grating formation in azopolymer thin films. The model allows us to explain the mechanism of spontaneous patterning, and self-organization. It allows us to compute the surface relief profile and its evolution, with good agreement with experiments.
[en] This paper studies the surface instability of an elastic thin solid film lying on a rigid substrate and subjected to van der Waals-like surface interactions. The effect of film-substrate interfacial slippage is accounted for by using a simplified linear cohesive interface model. It is found that the interfacial slippage generally plays a destabilizing role in the surface instability of the thin film. For highly compressible films with Poisson's ratio smaller than 0.25, the surface wrinkling behaviour previously inconceivable in the case of a perfectly bonded interface is now feasible if film-substrate interface slipping is permitted. In addition, our linear perturbation analysis shows that the critical conditions for the onset of surface instability can be modulated by adjusting the slippery stiffness of the interface. The result might be helpful for developing novel techniques to create micro-/nanosized surface patterns.
[en] The precise control of the structure and related properties becomes crucial for sophisticated applications of thin films deposited by magnetron sputtering in emerging industries including the flat panel display, digital electronics and nano- and bio-industries. The film structure is closely related to the total energy delivered to the substrate surface for nucleation and growth during all kinds of thin film processes, including magnetron sputtering. Therefore, the energy delivered to the surface for nucleation and growth during magnetron sputtering should be measured and analysed by integrated diagnostics of the plasma parameters which are closely associated with the process parameters and other external process conditions. This paper reviews the background of thin film nucleation and growth, the status of magnetron sputtering technology and the progress of plasma diagnostics for plasma processing. The evolution of the microstructure during magnetron sputtering is then discussed with respect to the change in the process variables in terms of the plasma parameters along with empirical data of the integrated plasma diagnostics for various magnetron sputtering conditions with conventional dc, pulsed dc and high power pulsed dc sputtering modes. Among the major energy terms to be discussed are the temperature change in the top surface region and the energies of ions and neutral species. (topical review)
[en] We study the quantum forces that act between two nearby conductors due to electronic tunnelling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunnelling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results