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Cleri F.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
International Journal of Plasticity | Year: 2012

We present a continuum model describing the extreme plastic behavior of nanostructured materials with covalent bonding, drawing inspiration both from recent experiments on Si nanowires, and atomic-scale molecular dynamics simulations. Building on the observations of such works it is proposed that deformation in a nanostructure made of randomly oriented nanocrystals embedded in an amorphous layer, proceeds by transferring the deformation energy to and from three distinct regions: a crystalline phase, corresponding to the bulk-like interior of each nano grain; a constrained amorphous phase, the percolative connecting network between different nano grains; and a defect accumulation zone, a thin shell surrounding each nano grain, where matter is turned from one phase into another. We formulate a free energy functional to describe the energy balance among the phases under steady non-equilibrium loading conditions. Strain and stress partial differential equations are derived, which are solved numerically to follow the evolution of the concentrations of the material phases, and the overall mechanical response of the system at constant input of external work. Matter transport is also included in the model, to account for stress-assisted diffusion, leading to accretion and non-constant volume and mass of the nanostructure during the mechanical deformation. A remarkable agreement with recent experiments on Si nanowires under extreme tensile deformation is obtained. © 2012 Elsevier Ltd. All rights reserved.

Arscott S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Applied Physics Letters | Year: 2013

Wetting of sessile bubbles on various wetting surfaces (solid and liquid) has been studied. A model is presented for the apparent contact angle of a sessile bubble based on a modified Young's equation - the experimental results agree with the model. Wetting a hydrophilic surface results in a bubble contact angle of 90°whereas using a superhydrophobic surface one observes 134°. For hydrophilic surfaces, the bubble angle diminishes with bubble radius whereas on a superhydrophobic surface, the bubble angle increases. The size of the plateau borders governs the bubble contact angle, depending on the wetting of the surface. © 2013 AIP Publishing LLC.

Pi X.,Zhejiang University | Delerue C.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Physical Review Letters | Year: 2013

We present tight-binding calculations in the random-phase approximation of the optical response of Silicon nanocrystals (Si NCs) ideally doped with large concentrations of phosphorus (P) atoms. A collective response of P-induced electrons is demonstrated, leading to localized surface plasmon resonance (LSPR) when a Si NC contains more than ≈10 P atoms. The LSPR energy varies not only with doping concentration but also with NC size due to size-dependent screening by valence electrons. The simple Drude-like behavior is recovered for NC size above 4 nm. Si NCs containing a large number of deep defects in place of hydrogenic impurities do not give rise to LSPR. © 2013 American Physical Society.

Arscott S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

This short review focuses on the application of SU-8 for the microchip-based approach to the miniaturization of mass spectrometry. Chip-based mass spectrometry will make the technology commonplace and bring benefits such as lower costs and autonomy. The chip-based miniaturization of mass spectrometry necessitates the use of new materials which are compatible with top-down fabrication involving both planar and non-planar processes. In this context, SU-8 is a very versatile epoxy-based, negative tone resist which is sensitive to ultraviolet radiation, X-rays and electron beam exposure. It has a very wide thickness range, from nanometres to millimetres, enabling the formation of mechanically rigid, very high aspect ratio, vertical, narrow width structures required to form microfluidic slots and channels for laboratory-on-a-chip design. It is also relatively chemically resistant and biologically compatible in terms of the liquid solutions used for mass spectrometry. This review looks at the impact and potential of SU-8 on the different parts of chip-based mass spectrometry-pre-treatment, ionization processes, and ion sorting and detection. © 2014 the Partner Organisations.

Devos A.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Ultrasonics | Year: 2015

The aim of this paper is to review the various laser-wavelength effects reported in the field of ultrafast acoustics (UA). First observed by chance in 1999, a wavelength change can indeed have a strong effect on the signal detected in UA. After the physical origin of the effect was clarified and from a systematic exploration we established that all the opto-acoustic mechanisms acting in UA are influenced by the laser-wavelength. From that we suggested original applications of UA to fundamental and applied physics. So emerged a new field, now referred as Colored Picosecond Acoustics or APiC. © 2014 Elsevier B.V. All rights reserved.

Arscott S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
RSC Advances | Year: 2014

Electrowetting is coming to fruition for many applications such as display technologies, droplet transport, smart optics, flexible systems, remote switching, electronic paper, miniaturized chemistry and energy harvesting. Surprisingly, although most of the workings of this technology have been achieved using semiconductor fabrication techniques-electrowetting has yet to fully take advantage of the wealth of physical properties (electrical, optical, mechanical, thermal, magnetic...) offered by semiconducting materials. This short review paper is intended to bridge the gap a little between electrowetting and the possible use of semiconductor properties for novel applications involving liquids and technology. © 2014 The Royal Society of Chemistry.

Molina-Sanchez A.,CNRS Institute of Electronics, Microelectronics and Nanotechnology | Wirtz L.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We report ab initio calculations of the phonon dispersion relations of the single-layer and bulk dichalcogenides MoS2 and WS2. We explore in detail the behavior of the Raman-active modes A1g and E2g1 as a function of the number of layers. In agreement with recent Raman spectroscopy measurements, we find that the A1g mode increases in frequency with an increasing number of layers while the E2g1 mode decreases. We explain this decrease by an enhancement of the dielectric screening of the long-range Coulomb interaction between the effective charges with a growing number of layers. This decrease in the long-range part overcompensates for the increase of the short-range interaction due to the weak interlayer interaction. © 2011 American Physical Society.

Niquet Y.-M.,Institute Nanosciences et Cryogenie INAC | Delerue C.,CNRS Institute of Electronics, Microelectronics and Nanotechnology | Krzeminski C.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Nano Letters | Year: 2012

We investigate electron and hole mobilities in strained silicon nanowires (Si NWs) within an atomistic tight-binding framework. We show that the carrier mobilities in Si NWs are very responsive to strain and can be enhanced or reduced by a factor >2 (up to 5×) for moderate strains in the ±2% range. The effects of strain on the transport properties are, however, very dependent on the orientation of the nanowires. Stretched 〈100〉 Si NWs are found to be the best compromise for the transport of both electrons and holes in ≈10 nm diameter Si NWs. Our results demonstrate that strain engineering can be used as a very efficient booster for NW technologies and that due care must be given to process-induced strains in NW devices to achieve reproducible performances. © 2012 American Chemical Society.

Allard A.,CNRS Institute of Electronics, Microelectronics and Nanotechnology | Wirtz L.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Nano Letters | Year: 2010

The phonon dispersion of graphene is known to display two strong Kohn Anomalies (kinks) in the highest optical branch (HOB) at the high-symmetry points Λ and K [Piscanec, S.; et al. Phys. Rev. Lett. 2004, 93, 185503 ]. The phonon slope around the Kohn anomalies is related to the electron-phonon-coupling (EPC) with the graphene π bands. We show that this EPC, which has strong impact, for example, on Raman scattering and electron transport, can be strongly modified due to interaction with a metallic substrate. For graphene grown on a Ni(111) surface, a total suppression of the Kohn anomaly occurs; the HOB around Λ and K becomes completely flat. This is due to the strong hybridization of the graphene π-bands with the nickel d bands that lifts the linear crossing of the π bands at K. In addition, the out-of-plane modes are also found to be strongly affected by the binding to the substrate. For other metallic substrates, where the distance between the graphene sheet and the substrate is larger, hybridization is much less pronounced and the Kohn anomaly is only weakly perturbed. From experimental phonon dispersions, one can therefore draw conclusions about the interaction strength between graphene and its different substrates. © 2010 American Chemical Society.

Giordano S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
International Journal of Solids and Structures | Year: 2013

In this work we consider a cylindrical structure composed of a nonlinear core (inhomogeneity) surrounded by a different nonlinear shell (matrix). We elaborate a technique for determining its linear elastic moduli (second order elastic constants) and the nonlinear elastic moduli, which are called Landau coefficients (third order elastic constants). Firstly, we develop a nonlinear perturbation method which is able to turn the initial nonlinear elastic problem into a couple of linear problems. Then, we prove that only the solution of the first linear problem is necessary to calculate the linear and nonlinear effective properties of the heterogeneous structure. The following step consists in the exact solution of such a linear problem by means of the complex elastic potentials. As result we obtain the exact closed forms for the linear and nonlinear effective elastic moduli, which are valid for any volume fraction of the core embedded in the external shell.© 2013 Elsevier Ltd. All rights reserved.

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