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Now showing items 1 - 16 of 4838

  • Optimization of electrodes design for PZT thin-film actuated membranes

    Casset, F.   Michaud, H.   Ricart, T.   Le Rhun, G.   Cueff, M.   Abergel, J.   Ancey, P.   Faralli, D.   Devos, A.   Fanget, S.   Defay, E.  

    This paper reports on the optimization of electrodes design for sol-gel Pb(Zr-0.52, Ti-0.48)O-3 (PZT) thin-film actuatedmembranes. PZT can be used in many actuator applications such as micro mirror, RF MEMS, inkjet or loudspeaker due to its strong piezoelectric properties. We aim to design membrane-based actuators with the optimum electrode dimensions allowing the largest membrane displacement under a given actuation voltage. We present in this paper measurement results, in good agreement with the finite element modeling, proving that an actuator area between 50 and 60% of the membrane area exhibits the highest deflection. (C) 2012 Elsevier Ltd....Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.
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  • Pyroelectricity of Pb(Zr0.52Ti0.48)O-3 films grown by sol-gel process on silicon

    Moalla, R.   Le Rhun, G.   Defay, E.   Baboux, N.   Sebald, G.   Bachelet, R.  

    Pyroelectric Pb(Zr0.52Ti0.48)O-3 films have been grown by sol-gel process on Si(001). Intrinsic pyroelectric coefficient has been measured through ferroelectric loops recorded at different temperatures and is about -300 mu C/m(2)K. Corresponding converted pyroelectric power density is estimated to be similar to 1 mW/cm(3) for a temperature variation of 10 degrees C every 6 s. Pyroelectric response of these films has been confirmed by direct measurements of the pyroelectric current with temperature variations at zero electric field. These results are of high interest for integrated thermally-sensitive devices. (C) 2015 Elsevier B.V. All rights reserved.
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  • Integrated metallic gauge in a piezoelectric cantilever

    Cueff, M.   Delay, E.   Le Rhun, G.   Rey, P.   Perruchot, F.   Suhm, A.   Aid, M.  

    In this study, a self-sensitive piezoelectric cantilever with a new design for sensing is presented. Microcantilevers were actuated by a 120 nm-thick Lead Zirconate Titanate Oxide (PZT) layer. Detection was done by measuring the resistance of a metallic gauge integrated on the surface of the micro-piezoelectric cantilevers. Some metallic gauges were embedded in a Wheatstone bridge to improve the measured resistance accuracy. Devices with direct resistance measurement were also realized. Gauge resistance responses were compared with an optical measurement by a White Light Interferometer. By biasing the Pit between 5 V and 5 V. cyclic deflection of the cantilever was detected with both optical and metallic gauge resistance systems. The two measurements fit. This self-sensitive piezoelectric cantilever can be used for fatigue test with packaged devices. (C) 2011 Elsevier B.V. All rights reserved.
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  • Integrated piezoresistive gauge in a piezoelectric cantilever

    Cueff, M.   Defay, E.   Le Rhun, G.   Perruchot, P.   Suhm, A.   Aid, M.  

    In this study, a new design for self-sensitive MEMS cantilevers is presented. Cantilevers were actuated with a 120 nm-thick Lead Zirconate Titanate (PZT) layer. Detection was done by using an integrated piezoresistive gauge in top and bottom electrode. Some piezoresistive gauges were integrated in a Wheatstone bridge to improve the sensitivity. Devices with direct measurement gauge were also realized. Piezoresistive responses were compared with an optical measurement by a light interferometer. By poling the PZT between -5v and 5v, the ferroelectric cycle was observed with both optical and piezoresistive detections. The two measurement are fitting. This self-sensitive piezoelectric cantilever can be used for fatigue test with packaged devices. With this new design, piezoresistive gauge can be integrated without cost increase in piezoelectric devices because no technological steps are added for gauges realization. (C) 2010 Published by Elsevier Ltd.
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  • Chemistry of surface nanostructures in lead precursor-rich PbZr0.52Ti0.48O3 sol-gel films

    Gueye, I.   Le Rhun, G.   Gergaud, P.   Renault, O.   Defay, E.   Barrett, N.  

    We present a study of the chemistry of the nanostructured phase at the surface of lead zirconium titanate PbZr0.52Ti0.48O3 (PZT) films synthesized by sol-gel method. In sol-gel synthesis, excess lead precursor is used to maintain the target stoichiometry. Surface nanostructures appear at 10% excess whereas 30% excess inhibits their formation. Using the surface-sensitive, quantitative X-ray photoelectron spectroscopy and glancing angle X-ray diffraction we have shown that the chemical composition of the nanostructures is ZrO1.82-1.89 rather than pyrochlore often described in the literature. The presence of a possibly discontinuous layer of wide band gap ZrO1.82-1.89 could be of importance in determining the electrical properties of PZT-based metal-insulator-metal heterostructures. (C) 2015 Elsevier B.V. All rights reserved.
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  • In situ 2D diffraction as a tool to characterize ferroelectric and piezoelectric thin films

    Khamidy, N. I.   Kovacova, V.   Bernasconi, A.   Le Rhun, G.   Vaxelaire, N.  

    In this paper the application of 2D x-ray diffraction (XRD2) as a technique to characterize in situ during electrical cycling the properties of a ferroelectric and piezoelectric thin film is discussed. XRD2 is one type of XRD on which a 2D detector is used instead of a point detector. This technique enables simultaneous recording of many sample information in a much shorter time compared to conventional XRD. The discussion is focused especially on the data processing technique of the huge data acquired. The methodology to calculate an effective piezoelectric coefficient, analyze the phase and texture, and estimate the domain size and shape is described in this paper. This methodology is then applied to a lead zirconate titanate (PZT) thin film at the morphotropic phase boundary (MPB) composition (i.e. Pb[Zr0.52Ti0.48]O-3) with a preferred orientation of (1 0 0). The in situ XRD2 characterization was conducted in the European synchrotron radiation facility (ESRF) in Grenoble, France. Since a high-energy beam with vertical resolution as small as 100 nm was used, a cross-sectional scan of the sample was performed over the entire thickness of the film. From these experimental results, a better understanding on the piezoelectricity phenomena in PZT thin film at MPB composition were achieved, providing original feedback between the elaboration processes and functional properties of the film.
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  • Development and Characterization of a Piezoelectrically Actuated MEMS Digital Loudspeaker

    Dejaeger, R.   Casset, F.   Desloges, B.   Le Rhun, G.   Robert, P.   Fanget, S.   Leclere, Q.   Ege, K.   Guyader, J-L  

    The MEMS digital loudspeaker consists of a set of acoustic transducers, called speaklets, arranged in a matrix and which operate in a binary manner by emitting short pulses of sound pressure. Using the principle of additivity of pressures in the air, it is possible to reconstruct an audible sound. MEMS technology is particularly well suited to produce the large number of speaklets needed for sound reconstruction quality while maintaining a reasonable size. This paper presents for the first time the modeling, realization and characterizations of a piezoelectric digital loudspeaker based on MEMS technology. Static, dynamic and acoustic measurements are performed and match closely with theoretical results. (C) 2012 Elsevier Ltd....Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.
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  • Piezoelectric response hysteresis in the presence of ferroelastic 90 degrees domain walls

    Le Rhun, G.   Vrejoiu, I.   Alexe, M.  

    Piezoelectric response hysteresis curves of Pb(Zr0.2Ti0.8)O-3-based capacitors have been measured by piezoresponse force microscopy. The piezoelectric coefficient d(33) was found to vary considerably depending on the position of the probing tip on the top electrode for films possessing a c/a/c domain structure. d(33) values up to 125 pm/V, which is twice the theoretical value for a clamped film, have been measured. The spatial variations of the piezoelectric response amplitude is explained by a local movement of ferroelastic 90 degrees a domains. This work experimentally proves the local enhancement of the polarization near the 90 degrees wall boundaries, as predicted by Ishibashi.
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  • A model for fatigue in ferroelectric thin films based on trapping of carriers at interfacial states

    Le Rhun, G.   Poullain, G.   Bouregba, R.  

    Experimental data on fatigue in the Metal/Ferroelectric/Metal thin film structures are reported. A model is proposed based on the trapping and the releasing of the free carriers in the band-gap states located at the interfaces between the electrodes and the ferroelectric film. Fits of the experimental data with the plots calculated from the model show very good agreement. In particular, the fatigue dependence on both the frequency and the magnitude of the applied voltage is well reproduced by the model. Saturation of fatigue for a large number of cycles is also predicted
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  • Low-temperature fabrication of Ba(1-x)Sr(x)TiO(3) thin films with good dielectric properties on platinized silicon substrates

    Zhu, X. H.   Defay, E.   Guigues, B.   Le Rhun, G.   Dubarry, C.   Aid, M.  

    Ba(0.7)Sr(0.3)TiO(3) (BST) thin films 500 nm in thickness were prepared on technologically desirable Pt/TiO(2)/SiO(2)/Si(1 0 0) substrates by ion beam sputtering (IBS) and post-deposition annealing method. The effect of annealing temperature on the structural and dielectric properties of BST thin films was systematically investigated. A sharp transition in their tunable dielectric behaviours was observed in good agreement with the evolution of crystal structure from amorphous to crystalline phase. It was demonstrated that the perovskite phase could crystallize in BST films at a very low temperature, around 450 degrees C. The lowering of perovskite crystallization temperature in the BST films was explained in terms of the high energetic process nature of IBS technique. A high dielectric tunability of 42% at E (electric field intensity) = 500 kV/cm and a low loss tangent of 0.013 at zero bias were both obtained in the 450 degrees C-annealed film, thereby resulting in the highest figure-of-merit factor among all the different temperature annealed films. Moreover, the 450 degrees C-annealed film showed superior leakage current characteristics with a low leakage current density of about 10(-4) A/cm(2) at E = 800 kV/cm. (C) 2009 Elsevier Ltd. All rights reserved.
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  • Reply to G. Le Flahec et al

    Ngeow, Joanne; Eng, Charis  

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  • Reply to G. Le Flahec et al

    Stadler, Zsofia K.   Saltz, Leonard B.  

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  • Reply to G. Le Flahec et al

    Stadler, Zsofia K.; Saltz, Leonard B.  

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  • Reply to G. Le Flahec et al

    Ngeow, Joanne   Eng, Charis  

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  • ?le?ain the?g Veda?: Poetic Effects in?g VedaX.29.1

    Jamison   Stephanie W.  

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  • J. M. G. Le Clezio : L'indigene revolutionnaire

    Simpore, K.  

    Resume Dans le journal Le Monde du 7 Avril 2010, Le Clezio et Jean-Patrick Razon denoncaient avec vehemence un projet de GDF-Suez pour la realisation d'un barrage hydro-electrique, l'un des plus grands du Bresil. Bien que ce projet soit louable, il n'en demeure pas moins que les consequences liees a sa realisation soient des plus desastreuses sur le plan ecologique et humanitaire, mais aussi sur la population indigene amazonienne. Si la defense du bassin de la riviere Madeira constitue ici dans cette reflexion le point focal d'une action militante de Le Clezio, elle n'est cependant que l'expression d'un echantillon des valeurs profondes qu'incarnent l'auteur contre l'exploitation des peuples sans voix et de leur environnement. La technologie, moteur des economies performantes, nous interroge sur le seuil de tolerance qu'il faut consentir sur les degats que sa realisation engendre sur les indigenes et l'environnement.
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