Lattice strain and tilt mapping in stressed Ge microstructures using X-ray Laue micro-diffraction and rainbow-filtering

Micro-Laue diffraction and simultaneous rainbow-filtered micro-diffraction were used to measure accurately the full strain tensor and the lattice orientation distribution at the sub-micron scale in highly strained, suspended Ge micro-devices. A numerical approach to obtain the full strain tensor from the deviatoric strain measurement alone is also demonstrated and used for faster full strain mapping. We performed the measurements in a series of micro-devices under either uniaxial or biaxial stress and found an excellent agreement with numerical simulations. This shows the superior potential of Laue micro-diffraction for the investigation of highly strained micro-devices.Comment: 28 pages, 10 figure

New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

International audienceA new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1-1000 mbars and as a continuous flow cell for pressure lower than 10−3 mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd8Ni92(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules

Autoassemblage de monocouches organiques à faible température

A température ambiante, la plupart des monocouches constituées de molécules formées de chaînes alcanes présentent des phases caractérisées par la rotation des chaînes autour de leur axe moléculaire. Afin d obtenir un ordre cristallin, il est impératif de réduire l énergie du système. De nouvelles sous-phases liquides utilisant des agents cryoprotectifs permettent d accéder à des températures plus faibles que la température de glace de l eau. Les monocouches de surfactants tels que les acides gras ou les phospholipides ont été préparées à volume et pression surfacique constants. L étude de la stabilité des films par refroidissement a été effectuée par des isothermes de Langmuir et GIXOS et celle de l ordre dans le plan par GIXD. Les molécules adoptent des phases cristallines qui sont induites par un processus d autoassemblage d origine exclusivement entropique et dont la densité de compactage est similaire à celle d un monocristal à trois dimensions. La technique d XPCS a enfin été employée pour relier la dynamique de surface du système étudié à la formation des phases cristallines.At ambient temperature monolayer phases of most alkane chain molecules exhibit phases, characterised by the rotation of the chain around the molecular axis. Consequently, these phases are only weakly ordered rather than crystalline. In order to achieve crystalline ordering, the energy of the system needs to be reduced. New cryo-protective liquid subphases extend the accessible range to much lower temperatures than the freezing threshold of water. Monolayers of common surfactants like fatty acids and phospholipids were prepared under constant volume/constant surface pressure conditions and their phase behaviour was studied upon cooling. First insights into film stability and evolution upon cooling were achieved by Langmuir isotherms and GIXOS, while the in-plane ordering was investigated by GIXD. The molecules were found to adapt crystalline phases by a purely entropy driven self-assembly process, reaching packing densities similar to three dimensional single crystals. The evolution of the structure parameters compare to those of bulk alkanes undergoing the rotator-crystalline phase transition. XPCS was employed to relate the surface dynamics of the system to the appearance of crystalline phases. The phase transition was found to be accompanied by a change of the dynamics from propagating to overdamped capillary waves.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Dynamique des grandes échelles de la convection dans la photosphère solaire

TOULOUSE3-BU Sciences (315552104) / SudocTOULOUSE-Observ. Midi Pyréné (315552299) / SudocSudocFranceF

La modélisation des oscillations d'étoiles en rotation rapide

TOULOUSE3-BU Sciences (315552104) / SudocTOULOUSE-Observ. Midi Pyréné (315552299) / SudocSudocFranceF

Structural and Dynamical Properties of Water Confined in Highly Ordered Mesoporous Silica in the Presence of Electrolytes

International audienc

Micro-diffraction Investigation of Localized Strain in Mesa-etched HgCdTe Photodiodes

International audienc

Rapport I.13 Comparaison de résultats théoriques et expérimentaux pour une roue de pompe hélico-centrifuge

The paper gives the comparison between experimental measurements and theoretical flow calculations in an open mixed flow impeller. Various measurements from nominal flow Qn to partial flow .5 Qn show the velocity distribution in the impeller channels and boundary unsteady pressures around the impeller on the casing inner surface. Flow calculations from a quasi-tridimensional flow model are compared to measured values. The deviation may be considered as acceptable. The front casing unsteady pressure leads to an estimate of the energy exchange between the impeller main flow and the boundary flow initiated in the gap between the impeller blades and the front casing.L'étude présentée est une analyse comparée de résultats théoriques et expérimentaux obtenus pour une roue ouverte de pompe hélico-centrifuge. Les diverses mesures menées depuis le débit nominal Qn jusqu'à un débit partiel de 0,5 Qn mettent en évidence l'évolution du champ des vitesses et des pressions pariétales instationnaires en ceinture, ainsi que l'apparition des recirculations. La comparaison de ces mesures à des données théoriques, obtenues à partir d'un programme de calcul quasi-tridimensionnel montre une concordance acceptable. De même, l'analyse des pressions pariétales instationnaires donne une image des échanges d'énergie roue-fluide en ceinture.Huang X., Rieutord Émile, Spettel F., Lapray Jean-François. Rapport I.13 Comparaison de résultats théoriques et expérimentaux pour une roue de pompe hélico-centrifuge. In: Machines hydrauliques. Conception et exploitation. Développements récents et Applications aux différents secteurs industriels. Vingtièmes journées de l'hydraulique. Lyon, 4-6 avril 1989. Tome 1, 1989

Direct wafer bonding of amorphous or densified atomic layer deposited alumina thin films

International audienceSOI circuit exhibits excellent performance and rehabilitee but with the component miniaturization trend and the clock frequency increase, the self-heating phenomena that arise from the SOI structure itself must not be underestimated. In order to minimize this problem, several candidates have been identified to replace the buried silicon oxide (SiO2) by high thermal conductive dielectric layers such as HfO2, Si3N4, diamond or Al2O3. In order to elaborate a SOI structure using this kind of innovative buried dielectric, first of all, their direct bonding with silicon has to be studied. In this work, we investigate the bonding thermal behaviour of Si/Al2O3 and Al2O3/Al2O3 direct bonded structures: bondings are submitted to room temperature up to 900 A degrees C annealing. Amorphous or crystallized Al2O3 thin films were used in this study. Bonding energies are measured in an anhydrous atmosphere and bonding defectivity is analysed using scanning acoustic microscope (SAM). With amorphous a-Al2O3 layer, for T > 200 A degrees C, high bonding energy are obtained even if high defect density appeared when annealing temperature exceeded 400-500 A degrees C. Spontaneous debonding phenomena even occurred for a-Al2O3/a-Al2O3 direct bonding. This defectivity, unobservable using infrared camera, may be explained by chemical or structural Al2O3 modification such as gases desorption, internal stress or crystallisation state. Bonding with crystallized Al2O3 film has been also characterized by infrared spectroscopy and complementary analysis. No high defect density is observed with crystallized Al2O3 layer. Based on these results, an Al2O3 bonding mechanism is proposed