Papers by sandrine Gentil
The present invention therefore relates to a suspension for reflective coating of the lighting de... more The present invention therefore relates to a suspension for reflective coating of the lighting device, comprising the following elements diluted in an aqueous solvent: - a metal oxide as a reflector and having an average diameter of its particles of between 0.2 and 0.5 microns before incorporation - an amorphous alumina having: • a surface area comprised between 150 and 200m2 / g, • a pore volume of between 0.2 and 0.3 cm3 / g, • a pore size of between 2.5 and 3.5 nm, • a mean diameter amorphous alumina particles between 3 and 5 microns prior to incorporation, • a length / diameter ratio between 1.5 and 2, - a defoamer, the average diameter of particles of said coating suspension being between 0.05 and 0.09μm.
Microsystems, 2002
This chapter presents an overview on integration processes that have been developed for the fabri... more This chapter presents an overview on integration processes that have been developed for the fabrication of planar silicon structures coated by textured piezoelectric Pb(ZrxTi1−x)O3 (PZT) thin films. Key issues are the textured growth to achieve high piezoelectric coefficients and the stress compensation to control the bending of cantilevers as well as the stretching forces at membranes. Advanced dry etching techniques are needed for patterning the electrode films without damage to PZT, and without leaving residues. Some recent results on cantilever-microphone and piezoelectric micromachined ultrasonic transducer (pMUT) are presented.
MRS Proceedings, 2003
ABSTRACTAn high performance / inexpensive diskbender actuator was produced by combining efficient... more ABSTRACTAn high performance / inexpensive diskbender actuator was produced by combining efficient design and fabrication methods and a new technique to operate these actuators was developed and tested, which can enhance the displacement and force capabilities by almost a factor of 2 by using the same maximal driving voltage.The properties of these actuators are intermediate between those of standard bimorphs, used for very large displacements but providing rather small forces, and those of low voltage stack multilayers, which provide quite large forces but are generally heavier, larger and expensive for equivalent displacements. The absence of any external mechanical amplification mechanism and their geometry make these actuators particularly suitable for active vibration damping applications within buildings affected by perturbations of hundreds of μm or for noise control by emission of controlled sound in antiphase. The class of displacement/force, which can be obtained with suita...
Sensors and Actuators A: Physical, 2003
Physica B: Condensed Matter, 1999
ABSTRACT Optical spectra of Co2+ in LiCoPO4 are analysed theoretically by using a crystal-field H... more ABSTRACT Optical spectra of Co2+ in LiCoPO4 are analysed theoretically by using a crystal-field Hamiltonian of CS local symmetry. In this analysis the energy level scheme is determined. Crystal-field parameters are obtained. The influence of the spin-orbit interaction is also considered. Using symmetry considerations the polarised optical absorption spectrum in LiCoPO4 is briefly discussed. Calculations of the temperature dependence of magnetic susceptibility are performed using only a 4F basis. Calculated results are compared with experimental data and satisfactory agreement has been obtained.
Low Temperature Physics, 2002
The complete Raman spectra of a single crystal of LiNiPO4 for a wide temperature range are report... more The complete Raman spectra of a single crystal of LiNiPO4 for a wide temperature range are reported. Of the 36 Raman-active modes predicted by group theory, 33 have been detected. The spectra are successfully analyzed in terms of internal modes of the (PO4)3− group and external modes. Multiphonon Raman scattering is also discussed. Low-frequency lines, observed in the antiferromagnetic phase, are assigned to magnon scattering and are discussed briefly.
Journal of Applied Physics, 2004
By means of transmission electron microscopy (TEM) the structure of chemically ordered regions in... more By means of transmission electron microscopy (TEM) the structure of chemically ordered regions in Zr-doped Pb(Mg1∕3Ta2∕3)O3 has been studied. Large coherent ordered domains were obtained by the addition of 5mol%PbZrO3. The results obtained by conventional, analytical, and high-resolution TEM are consistent with the random-site description of the B-site order, the so-called random-layer model. Image simulations showed that a careful selection of the imaging conditions for high resolution transmission electron microscopy is necessary in order to determine the different B-site occupancies. By comparison of simulated with experimental images it was possible to directly distinguish between the different ordering models.
Journal of Applied Physics, 2000
In this communication we address two issues essential for low-voltage memory applications of ferr... more In this communication we address two issues essential for low-voltage memory applications of ferroelectric thin films: the size effect on polarization switching, and polarization fatigue. According to the proposed concept, both of these phenomena are controlled by local injection of charge into the interfacial layers of the ferroelectric film. In the experimental part of this work, we show that the entrapped charge relaxation can be enhanced by introducing a thin RuO2 layer into the top interface of the Pt/PZT/Pt ferroelectric capacitor. Capacitors prepared in this way using PZT with a 45/55 Zr/Ti ratio show a substantial improvement of fatigue performance and withstand relatively well the thickness downscaling. As a result, these capacitors exhibited good ferroelectric properties for driving voltage amplitudes as low as 0.6–0.8 V. Our results suggest that control of charge relaxation at the interface is a key issue for development of low-voltage ferroelectric capacitors.
Journal of Applied Physics, 2008
A shear mode resonator based on bulk waves trapped in c-axis oriented AlN thin films was fabricat... more A shear mode resonator based on bulk waves trapped in c-axis oriented AlN thin films was fabricated, simulated, and tested. The active 1.55 μm thick AlN layer was deposited on top of an acoustic Bragg reflector composed of SiO2/AlN λ/4 layer pairs. The resonance was excited by means of interdigitated electrodes consisting of 150 nm thick Al lines. Analytical and simulation calculations show that the in-plane electric field excites bulk acoustic wave shear modes that are trapped in such an AlN film slab. The experimental frequency corresponds well to the theoretical one. The evaluated resonance of the fundamental shear mode at 1.86 GHz revealed a coupling of 0.15% and Q-factor of 870 in air and 260 in silicon oil.
Japanese Journal of Applied Physics, 2000
Transparent single crystals of Pb(Zn1/3, Nb2/3)O3–PbTiO3 (PZN–PT) perovskite have been grown by t... more Transparent single crystals of Pb(Zn1/3, Nb2/3)O3–PbTiO3 (PZN–PT) perovskite have been grown by the slow cooling method in a temperature gradient furnace. The optimization of growth techniques to crystallize PZN–PT with a cubic habitus is described in details. The growth temperature range and cooling rates was carried out in different lead fluxes. Crystal recovery from the residual flux was obtained by different techniques based on liquid flux elimination at the end of the growth process. The best transparent single crystals of PZN–PT, obtained by a cooling at 0.8°C/h from 1150°C to 930°C, had a cubic habitus and a size of approx.: 4×4×2.5 mm3. The chemical composition and the homogeneity of the crystals were tested by electron probe micro-analysis. Crystals characterization was performed using polarized light microscopy and dielectric and piezoelectric measurements. Phase transitions were determined by differential scanning calorimetry, optical and dielectric measurements.
Integrated Ferroelectrics, 2000
ABSTRACT
Integrated Ferroelectrics, 2003
PZT (PbZrxTi1 − xO3) thin films have been locally grown by means of sol-gel deposition and local ... more PZT (PbZrxTi1 − xO3) thin films have been locally grown by means of sol-gel deposition and local annealing on microhotplates. The microhotplates were based on a stress compensated Si3N4/SiO2 membranes as structural elements and contained tantalum silicide filaments (Ta5Si3) for resistive heating. Above the filaments, a passivation layer of SiO2, an adhesion layer of Ti/TiO2 and a bottom electrode of
Physica B: Condensed Matter, 1999
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Papers by sandrine Gentil