Substrate effect on the magnetic microstructure of La0.7Sr0.3MnO3 thin films studied by magnetic force microscopy

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Electrochemiluminescence on-a-chip: towards a hand-held electrically powered optofluidic source.

International audienceWe report a microfluidic platform that integrates several parallel optical sources based on electrochemiluminescence (ECL) of 9,10-diphenylanthracene (DPA) as luminophore agent. The annihilation of DPA radicals provides a low wavelength emission at λ=430 nm in the blue-visible range. By varying the distance between electrodes for each ECL integrated source, this glass/PDMS/glass platform enabled a systematic investigation of the main electrochemical parameters involved in ECL. These parameters have been studied either in a static mode or in a dynamic one. Even at slow flow rate (~2 µl s(-1)), the renewal of electroactive species could be easily promoted inside the microfluidic channel which gives rise to a stable optical intensity for several minutes. Compared with traditional optically pumped dye sources, this microfluidic system demonstrates that ECL can be easily implemented on chip for producing much compact optofluidic sources. Such simply electrically powered system-on-chip would surely encourage the future of hand-held µTAS devices with integrated fast detection and embedded electronics

Polarised potential: Novel nanotech

International audienceScientists at the Laboratory for Photonics and Nanostructures have been developing a microfluidic device forthe control and measurement of electrokinetic phenomena that aims to blows previous models out of the water

Polarised potential: Novel nanotech

International audienceScientists at the Laboratory for Photonics and Nanostructures have been developing a microfluidic device forthe control and measurement of electrokinetic phenomena that aims to blows previous models out of the water

Extremely thin planarized grating for sub-diffraction (<100 nm) far-field optical imaging of living cell membranes

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Charge transfer and band gap opening of a ferrocene/graphene heterostructure

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Détermination des contraintes résiduelles et de la microstructure intra-granulaire dans des films minces de W déposés par pulvérisation magnétron

Intra-granular microstructure ($a_0$) and stress of tungsten rf magnetron sputtered thin films ($<$ 700 nm) have been correlated for deposits belonging to the T zone of the Tornton's microstructural diagram. The stress values determined from the curvature method are compared with those calculated from the XRD method in each diffracting phase ($\alpha$-W and $\beta$-W). The stress state is imposed by the rf magnetron sputtering poxer ($P$). The films deposited with a high $P$ are in a large compression stress state (in the $\alpha$-W phase) and own a free stress lattice parameter higher than the tungsten bulk one. We have quantitatively shown that the transition of the stress state from the compressive ($-1.7$ GPa) to the tensile one (0.9 GPa) was clearly explained by the intra-granular modification (diminution of the stress free lattice prarameter from 0.3164 nm). From the XRD experiments, we have measured the coherently diffracting domains and the microdistorsions, which respectively decrease and increase with the generation of compressive stresses in the films. In addition, we have observed the dependence of the $\beta$-W phase with the tension in the films.
Cet article concerne l'étude des propriétés mécaniques et microstructurales de films minces de tungstène (700 nm sur Si (100)) élaborés par pulvérisation magnétron en fonction de la puissance R.F. Les contraintes totales présentes dans les films (déterminées par la méthode de la flèche) sont très fortement influencées par la valeur de la puissance R.F. Elles varient de +1,2 GPa à $-1,5$ GPa pour des puissances de 350 W à 400 W. L'analyse par diffraction des rayons X a révélé la présence de phase $\beta$-W dans certains dépôts. Pour ces films, nous avons déterminé les contraintes dans chaque phase par la méthode des sin$^2~\psi$. Les mesures d'intensité intégrée des pics de diffraction nous ont permis d'évaluer la proportion des phases dans chaque film. Nous avons vérifié le bon accord, en appliquant la règle des mélanges, entre les valeurs des contraintes totales et celles calculées à partir des résultats de diffraction X. Nous avons montré que la présence de la phase $\beta$-W semble favorisée par un état de tension des films (jusqu'à 60 % en volume pour des dépôts en tension de +1,2 GPa). Le paramètre de maille libre de contrainte varie de façon spectaculaire. Il est très supérieur à celui du W massif pour les dépôts en compression (0,3173 nm au lieu de 0,3165 nm), et légèrement inférieur pour ceux en tension (0,3164 nm)

Computational study of velocity profile obtained in microfluidic channel bearing a fluidic transistor: toward highly resolved electrophoretic separation.

International audienceThe present work is a computational study of velocity profiles in microfluidic channels bearing field flow effect transistors (FFET). In particular, this work investigates perturbations and distortions of the sample band during electrophoretic transport in a rectangular separation channel. The EOF heterogeneity and its induced pressure render the predictions of the analytical performances rather complex. In this context, we propose a systematic numerical inquiry that focuses on the distribution of the velocities for several geometries and EOF modulations. We compare the calculated parabolic velocity profiles to the bare glass microchips. Here, the reported parabolic velocity profiles are coherent with recent experimental results that have been published elsewhere. From the presented equations, in such active hybrid microfluidic chip that integrates a FFET gate layer, separation can be optimized by playing on the gate coverage ratio. The flow fields obtained from analytical models allow further investigations about the efficiency and resolution during electrophoresis. The resulting induced pressure gradient and the associated band broadening underline the need to optimize the resolution in the detriment of the efficiency in such active microfluidic chips

Dielectric properties of a single nanochannel investigated by high-frequency impedance spectroscopy

International audienceHigh-frequency electric impedance spectroscopy is used to characterize the dielectric properties of a singlenanochannel in a micro/nanofluidic device. The simulated electric impedance results lead to the determinationof two conductance regimes, a non-ideal capacitance and its surface charge

Influence of the atomic nitrogen content in amorphous carbon nitride thin films on the modulation of their polarizable interfaces properties

International audienceAmorphous carbon nitride (a-CNX) thin films possessing different nitrogen contents (0.12 ≤ x ≤ 0.30) have been synthetized by the DC cathodic reactive magnetron sputtering technique on transparent glass/indium tin oxide (ITO) substrates. They were characterized ex-situ by using two microscopy techniques: scanning electron microscopy (SEM) and atomic force microscopy (AFM), a spectroscopic technique: X-ray photoelectron spectroscopy (XPS), and in solution by using electrochemical methods: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results obtained with these methods have permitted to highlight why a-CN0.30, the a-CNx sample with the highest nitrogen content among those investigated in this work, behaves both as a dielectrical material (low electronic conductivity) and as an ideally polarizable interface (high polarization resistance). For this purpose, the role of both the ionic strength and the overpotential were investigated in blocking electrode conditions, i.e. only in the presence of the supporting electrolyte. It was observed that the interfacial capacitance can be strongly electrically modulated with the ionic charge concentration and with the applied overpotential. The understanding of the behaviour of a-CNx materials presents a great challenge for their integration in new microfluidic transistor type devices in view of the elaboration of polarizable interface flow-field effect transistors (PI-FFETs)