Michel Troyon
University of Reims Champagne-Ardenne
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Michel Troyon.
Nanotechnology | 1997
Michel Troyon; Z Wang; D Pastre; H N Lei; A Hazotte
Force modulation microscopy via sample displacement has been used to image the elastic characteristics of a stiff material - a nickel-based superalloy in which the two phases have close Youngs moduli. The experimental operating conditions for obtaining good images are such that the hypothesis of a linear tip - sample interaction is difficult to satisfy when stiff samples are involved, more difficult for a given static load than with compliant materials. To limit the undesirable effects of friction, the cantilever deflection amplitude must be kept small and the modulation frequency must be chosen outside a resonance of the system, but high enough to generate a strong dynamic load able to sufficiently indent the sample. A semiquantitative approach of the elasticity measurement taking into account the nonlinearity of the tip - sample interaction is proposed and described. The semiquantitative term is understood here as the possibility of measuring the elastic modulus of one of the constituents of a material relative to another constituent, the Youngs modulus of which is known and used as a reference.
ChemPhysChem | 2012
Marya Hardzei; Mikhail Artemyev; Michael Molinari; Michel Troyon; Alyona Sukhanova; Igor Nabiev
Fluorescence resonance energy transfer (FRET) in conjugates of CdSe-ZnS semiconductor nanocrystals of different shapes (FRET donors) and an Alexa Fluor organic dye (FRET acceptors) is examined. The dye molecules are chemically conjugated with quantum dots (QDs) or nanorods (NRs) in dimethyl sulfoxide colloidal solutions, and FRET efficiency in the purified conjugates is measured. The FRET from NR to a single dye molecule is less efficient than that of the QD-dye conjugates and this effect is explained in terms of distance-limited energy-transfer rate in the case of a point-like acceptor and extended donor dipoles. However, the larger surface area of NRs allows for many more dye acceptors to be bound, and the total FRET efficiency in NR-dye conjugates approaches those of QD-dye conjugates.
Applied Physics Letters | 2011
Nicolas Bouchonville; Michael Molinari; Alyona Sukhanova; Mikhail Artemyev; Vladimir Oleinikov; Michel Troyon; Igor Nabiev
The fluorescence resonance energy transfer (FRET) between quantum dots (QDs) and photochromic protein bacteriorhodopsin within its natural purple membrane (PM) is explored to monitor their assembling. It is shown that the efficiency of FRET may be controlled by variation of the surface charge and thickness of QD organic coating. Atomic force microscopy imaging revealed correlation between the surface charge of QDs and degree of their ordering on the surface of PM. The most FRET-efficient QD-PM complexes have the highest level of QDs ordering, and their assembling design may be further optimized to engineer hybrid materials with advanced biophotonic and photovoltaic properties.
Journal of Applied Physics | 2003
Franck H. Lei; J.-L. Nicolas; Michel Troyon; Ganesh D. Sockalingum; S. Rubin; Michel Manfait
An improved nonoptical shear force detection system based on a rectangular bimorph cantilever incorporating the force feedback technique has been developed for tip–sample distance regulation in shear force microscopy. The force feedback amplifier consisting of a phase shifter and a linear amplifier is adjusted in such a way that the motion of the cantilever is mechanically amplified, resulting in a great enhancement of quality factor Q. Driving a fiber attached bimorph cantilever at its first harmonic resonance, with a phase shift φ=π/2 and an appropriate amplifier gain, allows one to obtain a Q factor greater than 103 in air, which corresponds to a Q enhancement of more than 1 order of magnitude. The effect of Q enhancement leads to an increase in the signal to noise ratio and thus the force detection sensitivity of the system. Typically, the minimum interaction force that can be sensed by the system is about 2 pN/√Hz. Topographic images of a human aorta tissue section in its natural state, taken with th...
Journal of Applied Physics | 2008
A. El Hdiy; K. Gacem; Michel Troyon; A. Ronda; F. Bassani; I. Berbezier
We are interested in germanium nanocrystal density and size effects on the carrier storage and emission processes. For this purpose, high frequency capacitance-voltage and current-voltage characteristics were performed for temperatures varying from 300 to 77 K. Ge nanocrystals were deposited on a silicon dioxide/p-doped silicon structure and capped with a thin amorphous silicon layer. Results evidenced an electron storage phenomenon in nanocrystals that presented two different behaviors depending on the temperature. For temperatures higher than ∼140 K, the storage was mainly controlled by the nanocrystal density. At low temperatures the storage was reduced due to lowering of the tunneling barrier that resulted from a carrier quantum confinement process. Thermal activation energy of the carrier emission process was revealed as varying linearly with nanocrystal energy band gap. Activation energy was identified as a barrier height to be overcome by the emitted electrons.
Philosophical Magazine | 2006
Michel Troyon; Sébastien Lafaye
In the Sneddon relationship between unloading contact stiffness, elastic modulus and contact area, it is absolutely necessary to introduce a correction factor α to perform good elastic modulus and hardness measurements by nanoindentation. This is verified by comparing the contact area determined from the Sneddon equation in the usual way to the projected area of the residual indent measured by atomic force microscopy (AFM). For fused quartz indented by a sharp Berkovich indenter, the tip radius of which is 180 nm, an α value as high as 1.17–1.19 is evaluated for a load of 10 mN corresponding to a penetration depth of about 300 nm. This correction factor is not a constant having a single value valid for any Berkovich indenter, but strongly depends on the blunting state of the indenter when measurements are performed in the nanoindentation regime, i.e. penetration depths of the order of a few hundreds nanometres.
Applied Physics Letters | 2001
Franck H. Lei; G. Y. Shang; Michel Troyon; M. Spajer; H. Morjani; Jean-François Angiboust; Michel Manfait
Near-field fluorescence spectra with subdiffraction limit spatial resolution have been taken in the proximity of mitochondrial membrane inside breast adenocarcinoma cells (MCF7) treated with the fluorescent dye (JC-1) by using a scanning near-field optical microscope coupled with a confocal laser microspectrofluorometer. The probe–sample distance control is based on a piezoelectric bimorph shear force sensor having a static spring constant k=5 μN/nm and a quality factor Q=40 in a physiological medium of viscosity η=1.0 cp. The sensitivity of the force sensor has been tested by imaging a MCF7 cell surface.
Applied Physics Letters | 2006
G. Saint-Girons; G. Patriarche; A. Michon; G. Beaudoin; I. Sagnes; Kacem Smaali; Michel Troyon
This letter reports on the growth mechanism of the InP cap layer over InAs∕InP quantum dots (QDs) fabricated by metal organic vapor phase epitaxy (MOVPE). QD edges are shown to act as preferential nucleation sites for the InP cap layer, leading to the formation of InP domains around the nanostructures. As∕P exchange reactions are at the origin of the planarization of the top of the QDs under P-rich ambient, thus leading to a final QD height equal to the local thickness of the InP cap layer. The possibility to use As∕P exchange reactions to homogenize the height distribution of MOVPE grown InAs∕InP QDs is discussed on the basis of these observations.
Applied Physics Letters | 2006
Kacem Smaali; Michel Troyon; A. El Hdiy; Michael Molinari; G. Saint-Girons; G. Patriarche
Conductive atomic force microscopy has been used to study the topography and the electric properties of InAs quantum dots (QDs) grown by metal organic vapor phase epitaxy on a n-type InP(001) substrate and covered with a 5nm thick InP cap layer. Images reveal that the cap layer has not entirely covered the surface, but has formed rounded terracelike structures surrounding the QDs. A high current is detected on the QDs, about ten times less on the terraces, and not detectable on the wetting layer. Charges can be trapped inside the QDs and the surrounding terraces in forward bias conditions with a temporary memory effect and discharged in reverse bias.
Journal of Applied Physics | 2007
K. Gacem; A. El Hdiy; Michel Troyon; I. Berbezier; Pierre-David Szkutnik; A. Karmous; A. Ronda
Germanium nanocrystals embedded in amorphous silicon and self-organized on a tunnel silicon dioxide layer thermally grown on (100) p-doped silicon substrate have been electrically studied at different temperatures by using current-voltage and capacitance-voltage measurements. Results showed a carrier exchange between the gate and isolated germanium nanocrystals via amorphous silicon. Hysteresis loops observed in the capacitance-voltage curves were attributed to electron injection∕emission process in germanium nanocrystals, which indicated a memory effect behavior. Resonant tunneling effect through germanium nanocrystals with large voltage gaps was observed at room temperature in these ultradense Ge nanocrystals of ∼3.5nm mean size. It appeared for increasingly low voltages when the temperature decreases. All these results are consistent with a Coulomb blockade effect in ultrasmall Ge nanocrystals in which an effective number of electrons transported by each tunneling step varied between 1.8 and 3.81.