28 papers (2009-...)

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Because of capillary condensation, water droplets appear in nano/micropores. The large associated surface interactions can deeply influence macroscopic properties as in granular media. We report that dynamical properties of such nanobridge dramatically change when probed at different time scales. Using a novel AFM mode, the Force Feedback Microscopy, the gap between the nanotip and the surface is continuously varied, and we observe this change in the simultaneous measurements, at different frequencies, of the stiffness G'(N/m), the dissipative coefficient G"(kg/sec) together with the static force. As the measuring time approaches the microsecond, the liquid droplet exhibits a large positive stiffness (it is small and negative in the long time limit). Although clearly controlled by surface effects, it compares to the stiffness of a solid nanobridge with a 1 GigaPa Young modulus. We argue that as evaporation and condensation gradually lose efficiency, the contact line progressively becomes immobile, which explains this behavior.

27- System analysis of force feedback microscopy
MS Rodrigues, L Costa, J Chevrier, F Comin
Journal of Applied Physics 115 (5), 054309-054309-6, 2014

PLoS ONE 9(7): e101687 (2014)
Luca Costa, Mario S. Rodrigues, Núria Benseny-Cases, Véronique Mayeaux,Joël Chevrier, Fabio Comin

The mechanical properties of PC12 living cells have been studied at the nanoscale with a Force Feedback Microscope using two experimental approaches. Firstly, the local mechanical impedance of the cell membrane has been mapped simultaneously to the cell morphology at constant force. As the force of the interaction is gradually increased, we observed the appearance of the sub-membrane cytoskeleton. We shall compare the results obtained with this method with the measurement of other existing techniques. Secondly, a spectroscopic investigation has been performed varying the indentation of the tip in the cell membrane and consequently the force applied on it. 
In contrast with conventional dynamic atomic force microscopy techniques, here the small oscillation amplitude of the tip is not necessarily imposed at the cantilever first eigenmode. This allows the user to arbitrarily choose the excitation frequency in developing spectroscopic AFM techniques. The damping coefficient is reproducibly observed to decrease when the excitation frequency is increased. 

The optical transmission and reflection in between two metalized optical fiber tips is studied in the optical near-field and far-field domains. Besides aluminum-coated tips for near-field scanning optical microscopy (NSOM), specifically developed gold-coated fiber tips cut by focused ion beam (FIB) are investigated. Transverse transmission maps of sub-wavelength width clearly evidence optical near-field coupling between the tips for short tip distances and becomes essentially Gaussian-shaped for larger distances in the far-field regime. Moreover concentric reflection fringes observed for NSOM-type tips illustrate the influence of the receiving fiber tip on the emission pattern of the source tip.

24- Comparison between Atomic Force Microscopy and Force FeedbackMicroscopy static force curves
Luca Costa, Mario S. Rodrigues, Simon Carpentier, Pieter Jan van Zwol, Joel Chevrier, Fabio Comin
Atomic Force Microscopy (AFM) conventional static force curves and Force Feedback Microscopy (FFM) force curves acquired with the same cantilever at the solid/air and solid/liquid interfaces are here compared. The capability of the FFM to avoid the jump to contact leads to the complete and direct measurement of the interaction force curve, including the attractive short-range van der Waals and chemical contributions. Attractive force gradients five times higher than the lever stiffness do not affect the stability of the FFM static feedback loop. The feedback loop keeps the total force acting on the AFM tip equal to zero, allowing the use of soft cantilevers as force transducers to increase the instrumental sensitivity. The attractive interactions due to the nucleation of a capillary bridge at the native oxide silicon/air interface or due to a DLVO interaction at the mica/deionized water interface have been measured. This set up, suitable for measuring directly and quantitatively interfacial forces, can be exported to a SFA (Surface Force Apparatus).

23-Imaging material properties of biological samples with a Force Feedback Microscope
Luca Costa, Mario S Rodrigues, Emily Newman, Chloe Zubieta, Joel Chevrier, Fabio Comin
Journal of Molecular Recognition 26.12 (2013): 689-693
Mechanical properties of biological samples have been imaged with a force feedback microscope. The force, force gradient and the dissipation are simultaneously measured quantitatively from solely the knowledge of the spring constant. The results are preliminary but demonstrate that the method can be used to measure material properties, it is robust and produce quantitative high force resolution measurements of interaction characteristics. The small stiffness and oscillation of the cantilever results in an vibrational energy much smaller than the thermal energy, reducing the interaction to a minimum. Because the lever is over-damped, the excitation frequency can be chosen arbitrarily. 
P.J. van Zwol, S. Thiele, C. Berger, W. A. de Heer, J. Chevrier
Owing to its two-dimensional electronic structure, graphene exhibits many unique properties. One of them is a wave vector and temperature dependent plasmon in the infrared range. Theory predicts that due to these plasmons, graphene can be used as a universal material to enhance nanoscale radiative heat exchange for any dielectric substrate. Here we report on radiative heat transfer experiments between SiC and a SiO2 sphere that have nonmatching phonon polariton frequencies, and thus only weakly exchange heat in near field. We observed that the heat flux contribution of graphene epitaxially grown on SiC dominates at short distances. The influence of plasmons on radiative heat transfer is further supported with measurements for doped silicon. These results highlight graphene’s strong potential in photonic near field and energy conversion devices.

21- Why do Atomic Force Microscopy force curves still exhibit jump to contact?
Mario S. Rodrigues, Luca Costa, Joel Chevrier and Fabio Comin
Appl. Phys. Lett. 101, 203105 (2012)
The force between two particles as a function of distance is one of the most fundamental curves in physics. Here we describe how the Force Feedback Microscope can routinely measure the tip-surface interaction in the entire range of distances with a sensitivity of 1 pN and in different media. The method allows to measure simultaneously the force, force gradient and damping from solely the knowledge of the lever spring constant. The jump to contact is avoided and thus it is possible to follow the brutal nucleation of a water bridge between the tip and the surface.

20-Tuning near field radiative heat flux through surface excitations with a metal insulator transition
P.J. van Zwol, L. Ranno, J. Chevrier
Phys. Rev. Lett. 108234301 (2012) – Published June 7, 2012
The control of heat flow is a formidable challenge due to lack of good thermal insulators. However as a result of progress made for radiative heat transfer in near field it was recently theoretically predicted that, by tuning electronic excitations on surfaces, large radiative heat flow contrasts, and thus better control of heat flow, may be achieved. Here we show experimentally that the phase transition of VO2 entails a change of surface polariton states that significantly affects radiative heat transfer in near field. In addition we observed a strong dependence of the farfield limit on the VO2 layer thickness. We found that in all cases the Derjaguin approximation correctly predicted radiative heat transfer in near field, but it underestimated the farfield limit. Our results indicate that a large contrast in heat flow can be realized in near field that is otherwise not attainable inside bulk material or in farfield.

It is shown that a graphene layer on top of a dielectric slab can dramatically influence the ability of this dielectric for radiative heat exchange turning a poor heat emitter/absorber into a good one and vice versa. The effect of graphene is related to thermally excited plasmons. The frequency of these resonances lies in the terahertz region and can be tuned by varying the Fermi level through doping or gating. It makes possible the fast modulation of the heat flux by electrical means, which opens up new possibilities for very fast manipulations with the heat flux. The heat transfer between two dielectrics covered with graphene can be larger than that between best known materials and becomes especially efficient below the room temperature.

JOURNAL OF APPLIED PHYSICS 111, 063110 (2012) 

P. J. van Zwol, L. Ranno, and J. Chevrier

Institut Ne ́el, CNRS and Universite Joseph Fourier Grenoble, BP 166 38042, Grenoble Cedex 9, France

(Received 19 January 2012; accepted 20 February 2012; published online 28 March 2012)

We show that functionalized micromechanical bilayer levers can be used as sensitive probes to accurately measure radiative heat flux in vacuum between two materials at the micro scale. By means of calibration to one material these measurements can be made quantitative for radiative heat flux or for either temperature or material emissivity. We discuss issues and opportunities for our method and provide ample technical details regarding its implementation and demonstrate good correspondence with the Stefan Boltzmann law. We use this system to probe the phase transition of VO2 and find that radiative heat transfer in farfield between VO2 and glass can be reversibly modulated by a factor of 5.

Virtual Journal of Nanoscale Science & Technology -- April 9, 2012

17- Casimir force measurements in Au-Au and Au-Si cavities at low temperature

PHYSICAL REVIEW B 85, 035426 (2012) 

J. Laurent, H. Sellier, A. Mosset, S. Huant, and J. Chevrier

Institut Ne ́el, CNRS et Universite ́ Joseph Fourier, B.P. 166, F-38042 Grenoble, Cedex 9, France

(Received 21 September 2011; revised manuscript received 16 December 2011; published 18 January 2012)

We report on measurements of the Casimir force in a sphere-plane geometry using a cryogenic force microscope to move the force probe in situ over different materials. We show how the electrostatic environment of the interacting surfaces plays an important role in weak force measurements and can overcome the Casimir force at large distance. After minimizing these parasitic forces, we measure the Casimir force between a gold-coated sphere and either a gold-coated or a heavily doped silicon surface in the 100–400 nm distance range. We compare the experimental data with theoretical predictions and discuss the consequence of a systematic error in the scanner calibration on the agreement between experiment and theory. The relative force over the two surfaces compares favorably with theory at short distance, showing that this Casimir force experiment is sensitive to the dielectric properties of the interacting surfaces.

16-Fast nanoscale heat-flux modulation with phase-change materials

Phys. Rev. B 83, 201404(R) (2011) [4 pages]
P. J. van Zwol, K. Joulain, P. Ben Abdallah, J. J. Greffet, and J. Chevrier

1Institut Néel, CNRS and Université Joseph Fourier Grenoble, Boîte Postale 166, FR-38042 Grenoble Cedex 9, France
We introduce a concept for electrically controlled heat-flux modulation. A flux contrast larger than 10 dB is expected with switching time on the order of tens of nanoseconds. Heat-flux modulation is based on the interplay between radiative heat transfer at the nanoscale and phase-change materials. Such large contrasts are not obtainable in solids, or in far field. As such, this opens up new horizons for temperature modulation and actuation at the nanoscale.

15-Phonon polaritons enhance near-field thermal transfer across the phase transition of VO2
P. J. van Zwol, K. Joulain, P. Ben-Abdallah, and J. Chevrier
Phys. Rev. B 84, 161413 (2011) – Published October 27, 2011
We show numerically that near-field heat flux can be modulated by orders of magnitude upon switching from the metallic to the insulating phase of vanadium dioxide. Furthermore, the resonant phonon polariton interaction for the insulating phase enhances near-field thermal transfer by three orders of magnitude. The effect should therefore be measurable with existing experimental setups and could find broad applications for systems where thermal control at the nanoscale is required.

14-Large Variation in the Boundary-Condition Slippage for a Rarefied Gas Flowing between Two Surfaces
J. Laurent, A. Drezet, H. Sellier, J. Chevrier, and S. Huant
Phys. Rev. Lett. 107, 164501 (2011) – Published October 11, 2011
Received 14 April 2011; published 11 October 2011
We study the slippage of a gas along mobile rigid walls in the sphere-plane confined geometry and find that it varies considerably with pressure. The classical no-slip boundary condition valid at ambient pressure changes continuously to an almost perfect slip condition in a primary vacuum. Our study emphasizes the key role played by the mean free path of the gas molecules on the interaction between a confined fluid and solid surfaces and further demonstrates that the macroscopic hydrodynamics approach can be used with confidence even in a primary vacuum environment where it is intuitively expected to fail.

13-“Negative” Backaction Noise in Interferometric Detection of a Microlever
J. Laurent, A. Mosset, O. Arcizet, J. Chevrier, S. Huant, and H. Sellier
Phys. Rev. Lett. 107, 050801 (2011) – Published July 28, 2011
Interferometric detection of mirror displacements is intrinsically limited by laser shot noise. In practice, however, it is often limited by thermal noise. Here we report on an experiment performed at the liquid helium temperature to overcome the thermal noise limitation and investigate the effect of classical laser noise on a microlever that forms a Fabry-Perot cavity with an optical fiber. The spectral noise densities show a region of “negative” contribution of the backaction noise close to the resonance frequency. We interpret this noise reduction as a coherent coupling of the microlever to the laser intensity noise. This optomechanical effect could be used to improve the detection sensitivity as discussed in proposals going beyond the standard quantum limit.

12-Living cell imaging by far-field fibered interference scanning optical microscopy
Jean-Baptiste Decombe, Wilfrid Schwartz, Catherine Villard, Herve Guillou, Joel Chevrier, Serge Huant, and Jochen Fick
Institut Néel, CNRS & Universite Joseph Fourier, Grenoble, France
Published 27 Jan 2011 (C) 2011 OSA 31 January 2011 / Vol. 19, No. 3 / OPTICS EXPRESS 2702We report on the imaging of biological cells including living neurons by a dedicated fibered interferometric scanning optical micro- scope. The topography and surface roughness of mouse fibroblasts and hippocampal neurons are clearly revealed. This straightforward far-field technique allows fast, high resolution observation of samples in liquids without lengthy alignment procedures or costly components.

11- Presence of electromagnetic fluctuations in micromechanics
Joël Chevrier
Comptes Rendus Physique, Volume 12, Issues 9–10, Pages 797-938 (December 2011) 
in Nano- and micro-optomechanical systemsNano- et micro-résonateurs optomécaniques 
Ed. A Heidmann
Micro electromechanical systems (MEMS) and mechanical effects of quantum fluctuations become strongly related. MEMS have allowed the production of important experimental results such as quantitative measurements of the Casimir force at the micro- and nanoscales. MEMS are used to probe these effects because they are sensitive to them and engineers will certainly have to increasingly consider the effects of quantum and thermal fluctuations in the design of MEMS that are used as actuators and sensors. These effects on MEMS are controlled by the electron–photon coupling. These questions are then coupled to new fields of research, such as photonics and plasmonics.

Aurélien Drezet, Alessandro Siria, Serge Huant, and Joël Chevrier
Phys. Rev. E 81, 046315 (2010) – Published April 23, 2010

It has been shown recently [ A. Siria, A. Drezet, F. Marchi, F. Comin, S. Huant and J. Chevrier Phys. Rev. Lett. 102 254503 (2009)] that in the plane-plane configuration, a mechanical resonator vibrating close to a rigid wall in a simple fluid can be overdamped to a frozen regime. Here, by solving analytically the Navier-Stokes equations with partial slip boundary conditions at the solid-fluid interface, we develop a theoretical approach justifying and extending these earlier findings. We show in particular that in the perfect-slip regime, the abovementioned results are, in the plane-plane configuration, very general and robust with respect to lever geometry considerations. We compare the results to those obtained previously for the sphere moving perpendicularly and close to a plane in a simple fluid and discuss in more details the differences concerning the dependence of the friction forces with the gap distance separating the moving object (i.e., plane or sphere) from the fixed plane. We show that the plane-plane geometry is more sensitive than the sphere-plane geometry for the measurement of slippage coefficients. Finally, we show that the submicron fluidic effect reported in the reference above, and discussed further in the present work, can have dramatic implications in the design of nanoelectromechanical systems.

9-Integration of an Atomic Force Microscope in a Beamline Sample Environment
M. S. Rodrigues, M. Hrouzek, O. Dhez, J. Chevrier, and F. Comin
AIP Conf. Proc. 1234, pp. 609-612
27 September–2 October 2009 Melbourne (Australia)
We developed and optimised an optics‐free Atomic Force Microscope (AFM) that can be directly installed on most of the synchrotron radiation end‐stations. The combination of Scanning Probe Microscopies with X‐ray microbeams adds new possibilities to the variety of synchrotron radiation techniques. The instrument can be used for atomic force imaging of the investigated sample or to locally measure the X‐ray absorption or diffraction, or it can also be used to mechanically interact with the sample while simultaneously taking spectroscopy or diffraction measurements. The local character of these measurements is intrinsically linked with the use of the Atomic Force Microscope tip. It is the sharpness of the tip that gives the opportunity to measure the photons flux impinging on it giving beam position monitor features, or allows to locally measure the absorption coefficient or the shape of the diffraction pattern. As an example of the possibilities opened by the instrument we will show diffraction measurements performed on a Ge∕Si island while being indented with the AFM tip providing local measure of the Young coefficient. Three ESRF beamlines are going to be equipped with this new instrument.
E. Rousseau, A. Siria, G. Jourdan, S. Volz, F. Comin, J. Chevrier & J.-J. Greffet
Nature Photonics 3, 514 - 517 (2009) 
Published online: 23 August 2009 | doi:10.1038/nphoton.2009.144
Heat can be exchanged between two surfaces through emission and absorption of thermal radiation. It has been predicted theoretically that for distances smaller than the peak wavelength of the blackbody spectrum, radiative heat transfer can be increased by the contribution of evanescent waves1, 2, 3, 4, 5, 6, 7, 8. This contribution can be viewed as energy tunnelling through the gap between the surfaces. Although these effects have already been observed9, 10, 11, 12, 13, 14, a detailed quantitative comparison between theory and experiments in the nanometre regime is still lacking. Here, we report an experimental setup that allows measurement of conductance for gaps varying between 30 nm and 2.5 m. Our measurements pave the way for the design of submicrometre nanoscale heaters that could be used for heat-assisted magnetic recording or heat-assisted lithography.
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7-Quantitative non-contact dynamic Casimir force measurements
G. Jourdan, A. Lambrecht, F. Comin and J. Chevrier
EPL 85 31001 2009 
We show that the Casimir force (CF) gradient can be measured with no contact involved. Results of the CF measurement with systematic uncertainty of 3% are presented for the distance range of 100–600 nm. The statistical uncertainty is shown to be due to the thermal fluctuations of the force probe. The corresponding signal-to-noise ratio equals unity at the distance of 600 nm. Direct contact between surfaces used in most previous studies to determine absolute distance separation is here precluded. Use of direct contact to identify the origin of distances is a severe limitation for studies of the CF on structured surfaces as it deteriorates irreversibly the studied surface and the probe. This force machine uses a dynamical method with an inserted gold sphere probe glued to a lever. The lever is mechanically excited at resonant frequency in front of a chosen sample. The absolute distance determination is achieved to be possible, without any direct probe/sample contact, using an electrostatic method associated to a real time correction of the mechanical drift. The positioning shift uncertainty is as low as 2 nm. Use of this instrument to probe a very thin film of gold (10 nm) reveals important spatial variations in the measurement.
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6-Viscous Cavity Damping of a Microlever in a Simple Fluid
A. Siria, A. Drezet, F. Marchi, F. Comin, S. Huant, and J. Chevrier
Phys. Rev. Lett. 102, 254503 (2009) – Published June 24, 2009

We consider the problem of oscillation damping in air of a thermally actuated microlever as it gradually approaches an infinite wall in parallel geometry. As the gap is decreased from 20  μm down to 400 nm, we observe the increasing damping of the lever Brownian motion in the fluid laminar regime. This manifests itself as a linear decrease in the lever quality factor accompanied by a dramatic softening of its resonance, and eventually leads to the freezing of the CL oscillation. We are able to quantitatively explain this behavior by analytically solving the Navier-Stokes equation with perfect slip boundary conditions. Our findings may have implications for microfluidics and micro- and nanoelectromechanical applications.

5-Probing the elastic properties of individual nanostructures by combining in situ atomic force microscopy and micro-x-ray diffraction
Scheler, T.; Rodrigues, M.; Cornelius, T. W.; Mocuta, C.; Malachias, A.; Magalhaes-Paniago, R.; Comin, F.; Chevrier, J.; Metzger, T. H.; 
Applied Physics Letters  Jan 2009 94 Issue:2 023109 - 023109-3
Atomic force microscopy (AFM) and micro-x-ray diffraction are combined to investigate nanostructures during in situ indentation. This technique allows the determination of elastic properties of individual nanoscale objects, particularly here SiGe/Si(001) self-assembled islands. Using this novel technique it was possible to select a specific island, align it in the microfocused beam, and apply a pressure onto it, using the AFM tip. Simultaneously, the x-ray diffuse scattering map from the island and the surrounding substrate was recorded in order to probe the lattice parameter change during indentation. An elastic reduction of the island lattice parameter of up to 0.6% was achieved.

4-In situ observation of the elastic deformation of a single epitaxial SiGe crystal by combining atomic force microscopy and micro x-ray diffraction
M. S. Rodrigues, T. W. Cornelius, T. Scheler, C. Mocuta, A. Malachias, R. Magalhães-Paniago, O. Dhez, F. Comin, T. H. Metzger, and J. Chevrier
J. Appl. Phys. 106, 103525 (2009)
An in situ combination of atomic force microscopy and micro x-ray diffraction was developed to study the elastic behavior of nanosized objects. This technique offers the means to locally access the Young elastic moduli and Poisson ratios of individual nanostructures. Here, we investigated the elastic behavior of a single self-assembled 450 nm high SiGe island. As pressure was applied on the island, the resonance frequency of the atomic force microscope tuning fork was tracked together with the x-ray diffraction stemming from this individual crystal. The change in the tip-island contact stiffness could be derived from the variation in the resonance frequency of the tuning fork, whereas the island mean lattice parameter was inferred from the center of mass of the island’s Bragg scattering. From this information, the reduced elastic modulus of the tip-island system could be directly determined, which is in very good agreement with literature values. The pressure needed to compress the island lattice to the Si value amounts to about 3 GPa and is in good accordance with finite-element method simulations of the displacement field in the pressurized object.

C. Mocuta, K. Mundboth, J. Stangl, B. Krause, A. Malachias, Th. Scheller, T. Cornelius, R. Paniago, A. Diaz, M. Rodrigues, J. Chevrier, O. Dhez, T.H. Metzger, G. Bauer, A. Barbier, A.V. Ramos, M.-J. Guittet, J.-B. Moussy, S. Stanescu, R. Mattana, C. Deranlot and F. Petroff. 
Revue de Métallurgie, 107 , pp 433-439  (2010)
In standard diffraction experiments, ensembles of objects are characterized yielding averaged, statistical properties (meaningful only if the ensemble is monodisperse). Focused x-ray beams are used here to localize single nanostructures, identifying and probing individual objects one by one. In a scanning mode, a 2-dimensional image of the sample is recorded, which allows the reproducible alignment of a specific nanostructure for analysis. The x-ray scattered signal is analyzed and modelled, to give access to the shape, strain and composition inside the single object with sub-micron resolution. Combination of x-ray microdiffraction technique with other micro-probe experiments on the very same individual object (simultaneous coupling of x-ray diffraction measurements with atomic force microscopy (AFM)) is also shown; we prove the possibility to interact with the objects and to address elastic properties for individual nano-structures out of an ensemble.

2-A Scheme for Solving the Plane–Plane Challenge in Force Measurements at the Nanoscale
A. Siria, S. Huant, G. Auvert, F. Comin, J. Chevrier
Nanoscale Res Lett (2010) 5:1360–1365 
Published online: 19 May 2010 
Non-contact interaction between two parallel flat surfaces is a central paradigm in sciences. This situa- tion is the starting point for a wealth of different models: the capacitor description in electrostatics, hydrodynamic flow, thermal exchange, the Casimir force, direct contact study, third body confinement such as liquids or films of soft condensed matter. The control of parallelism is so demanding that no versatile single force machine in this geometry has been proposed so far. Using a combination of nanopositioning based on inertial motors, of microcrystal shaping with a focused-ion beam (FIB) and of accurate in situ and real-time control of surface parallelism with X-ray diffraction, we propose here a ‘‘gedanken’’ surface-force machine that should enable one to measure interactions between movable surfaces separated by gaps in the micrometer and nanometer ranges.

1-A MEMS-based high frequency x-ray chopper
A Siria, O Dhez, W Schwartz, G Torricelli, F Comin and J Chevrier
Nanotechnology 20 175501 2009 
Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.