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La synthese hydrothermale permet la realisation de poudres fines cristallisees et desagglomerees Ces qualites sont appropriees a l'elaboration de composites fins oxyde/oxyde par synthese simultanee des deux phases. Nous avons developpe ce protocole pour la realisation de nanocomposites ahrmine/zircone (Q). Nous presentons ici plus particulierement le travail effectue sur la zircone, Les conditions de traitement hydrothermal et d'un traitement thermique modere supplementaire sont analysees en relation avec les caracteristiques des poudres synthetisees. Differentes techniques complementaires sont utilisees pour ces poudres de zircone: diffraction des rayons X (% de la phase quadratique, taille des cristallites), B.E.T. (surface specifique), pycnometrie helium (densite), morphologie (observations M.E.T.).

We have measured the interdiffusion coefficient at CdTeCd1 − xZnxTe interfaces by following the evolution of the X-ray diffraction patterns of superlattices annealed between 360 and 420°C under a Cd overpressure. A linear diffusion model is used to describe the experimental results. The interdiffusion coefficient is given by DCd (cm2/s) = 100 exp[−2.5 eV/kT]. The data agree well with the Cd self-diffusion coefficient measured by other techniques between 500 and 900°C. This shows that only one defect, probably the Cd vacancy, is involved in the diffusion process in bulk material and at CdTeCdZnTe interfaces. At growth temperature generally used for the molecular beam epitaxy of CdTe based superlattices (Tg ⩽ 280°C), the contribution of interdiffusion to the interface morphology can be neglected.

International audience; he appropriation process of the environmental space parameters by elders can be done through the use of color codes that are meaningful to the persons with loss of autonomy. This approach is based upon the natural interpretation of communicating signs and signals by the brain that helps to answer more quickly to critical situation at different degrees. We illustrate first with the transposition of the color codes used in the automobile domain to the housing environment. By extension, we show that intelligent furniture can be designed through ICT and home automation to assist persons with cognitive troubles or motor disability. Finally, we describe the application done in a dare care center for persons with cognitive troubles. Colors of the rooms have been chosen to allow the patients to naturally identify the role of each room.

International audience; The persons in loss of autonomy have several sociological and psychological blockings in using the technologies aimed to reduce their dependence. Thus, it is important to offer non neither intrusive nor stigmatizing solutions. It becomes necessary to propose schemes to allow these people to appropriate more easily the home automation and information technologies equipments installed in their housing environment. In our approach, we consider that the potential users of these technologies already had an automobile. We thus proposed the transfer of technologies initially dedicated to the automobile domain to the housing of the persons in loss of autonomy with the following concept: can the principles of communication, safety and protection used for the automobile be transposed to the housing context? The car manufacturers have created an effective descriptive system thanks to a green/orange/red visual code having a universal meaning. These colors were chosen because of the ability of the brain to get them quickly. The dashboard of the car perfectly integrates a set of logos based on these three colors. The brief appearance of a logo using one of these colors activates an immediate reaction of the person. Red means an immediate danger, orange call a greater surveillance and green is indicative and tolerant. The color code now overcomes the frame of the automobile and becomes a way of perceiving the environment in the daily life. It is thus interesting to study the transposition of this code and related logos to reduce the loss of autonomy. A possible application concerns the elders and the people affected by the Alzheimer's disease using the chromatic perception. In a first step, the association of the color code with the perception of the space allows to guide and to insure the fragile persons within their own environment. A second step consists in integrating chromic materials in the design of technological objects and items for the persons in loss of autonomy. The col! or of these smart materials changes reversibly according to various stimuli applied (heat, humidity, pressure, electricity, light ...). The red/orange/green code can then be chosen here also for a wide range of applications.

A range of studies, such as transmission electron microscopy, x-ray diffraction, and optical spectroscopy, applied to a series of CdTe/ZnTe superlattices with ultrathin ZnTe layers, confirmed the ability to grow, in CdTe, ultrathin pseudomorphic layers of ZnTe with limited Zn segregation and of high crystalline and optical quality, at least for layer thicknesses up to a few monolayers. Subsequently, we employed the spatially selective incorporation of monomolecular isoelectronic planes of ZnTe as a perturbative probe of the exciton states in a mixed-type CdTe/(Cd,Zn)Te superlattice. The effect of the ZnTe monolayer as a function of position on the heavy- and light-hole transitions of this system was determined by optical spectroscopy. Our results confirmed experimentally the type-I nature of the heavy-hole excitons and demonstrated the possibility to directly tune the ``indirectness'' of the light-hole exciton, depending on the position of the planar perturbation. Theoretical calculations were found in qualitative agreement with all these results.

This paper reviews the structural and optical properties of CdTe/Cd 1− x Zn x Te strained heterostructures grown by molecular beam epitaxy. Special attention is given to the control of strain and interface roughness and sharpness. It is shown that high quality superlattices are obtained with well width fluctuations on the monolayer scale. The electronic properties are also strain dependent, especially the valence band line-up. Two-dimensional exciton states are the dominant features of the optical spectra of CdTe/Cd 1− x Zn x Te quantum wells. By appropriate quantum well engineering, the exciton-phonon interaction is reduced and large room-temperature absorption observed.

Experiments have been designed to measure interdiffusion coefficients in CdTe/HgTe (001) superlattices grown by molecular beam epitaxy. The interdiffusion coefficients are deduced from double crystal X-ray diffraction on post-growth-annealed samples. The annealings are realized in the 200-240 degrees C range under Hg saturated pressure. The results indicate that interdiffusion is dependent on concentration. The authors calculate diffused profiles from an expression on D(c,T), and simulate the corresponding X-ray spectra to fit them with the experimental ones.

CdTe and Cd1−xZnxTe layers and microstructures were doped with indium donors during their growth at low temperatures (200–220 °C) by molecular‐beam epitaxy under Cd overpressure. Uniform and planar doping of layers and local doping of quantum wells and superlattices are presented. Characterization techniques include secondary‐ion mass spectroscopy (SIMS), capacitance‐voltage and Hall‐effect measurements, optical spectroscopy, x‐ray double diffraction, and x‐ray photoelectron spectroscopy. In the range of indium concentrations 2×1016–1×1018 cm−3, the donor activation efficiency is 100% for uniform doping. A low‐temperature carrier mobility of up to 5300 cm2/V s is obtained. The highest measured carrier concentration is 1.3×1018 cm−3; at a higher doping level, strong compensation occurs, related to dopant migration and cadmium vacancy formation. Planar doping also yields ≊100% activation efficiency for moderate values of sheet density (≊1011 cm−2) but has the same limit of about 1018 cm−3 for total carrier ...

Spectral measurements of the thermoluminescence from a polymineralic sand and its component minerals are reported. The signals from density-separated and chemically separated fractions of the sand are compared in an attempt to select wavelength regions characteristic of the quartz and feldspar mineral components. The data clearly demonstrate that for these materials the uses of conventional broad band optical filters and a blue sensitive photomultiplier tube fail to separate the mineral fractions, despite earlier claims. However, measurements in the near infra-red are characteristic of the feldspar components. Whilst density separations lead to clearly distinguishable spectral features for light, medium and heavy mineral fractions, subsequent HF etching and alpha irradiation emphasized that the TL of the density separated quartz fraction was dominated by the traces of feldspar contamination. Indeed, at the sensitivity level available, all the signal from the quartz fraction arose from traces of feldspar contaminants. The temperatures of the glow peaks are so similar in all mineral fractions that these values are a totally inadequate basis for mineral separation. The X-ray excited luminescence spectra differ from those of thermoluminescence but the blue/green radioluminescence is very similar for all the mineral fractions separated in this study. The similarity of radioluminescence and the glow peak temperatures are attributed to the role of the silicate groups, exciton decay paths and point defects in the silicate networks which are common to all the component minerals of feldspars, quartz, silica, zircon and silicates.

Experiments have been designed to measure the interdiffusion coefficients in CdTe/HgTe (001) superlattices grown by molecular beam epitaxy. The interdiffusion coefficients are deduced from double‐crystal x‐ray diffraction on samples annealed in the 200–240 °C range under a Hg saturated pressure. Our results indicate that the interdiffusion is strongly dependent on concentration with a coefficient given by D(CCd,T)=1.0 exp{[−1.45(±0.1) eV]/(kT)} exp {[−0.55 (±0.1) CCd eV]/(kT)} cm2/s. The activation energies ΔEHgTe≊1.45 eV and ΔECdTe≊2.0 eV are consistent with an interdiffusion process by a vacancy mechanism.

The optimal growth conditions to grow by molecular beam epitaxy CdxHg1−xTe/CdyHg1−yTe heterostructures (0.3

Spatially selective introduction of ultrathin ZnTe layers (1 to 3 monolayers) into CdTe allows the study of special superlattice structure, sponding to a monomolecnlar plane-host crystal system. Particular attention is given to the strain state control of the inserted ZnTe monolayer. High resolution electron microscopy is used to measure tle local lattice distortion: the method yields the location and the total amount of Zu per period, and the results are compared with X-ray diffraction data. Optical properties of these superlattices are also presented. All results show the ability to control ultrathin pseudomorphic layers of ZnTc within CdTe, witl limited Zn segregation, and of high crystalline and optical quality. In addition, they can be fitted within the framework of elasticity theory for the structural data, and of a finite quantum well model for the optical ones, even in the ultimate limit of only one nominal ZnTe monolayer. PACS numbers: 78.66.Hf, 73.61.Ga