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In the Cu–Fe–O phase diagram, delafossite CuFeO 2 is obtained for the Cu I oxidation state and for the Cu/Fe = 1 ratio. By decreasing the oxygen content, copper/spinel oxide composite can be obtained because of the reduction and the disproponation of cuprous ions. Many physical properties as for instance, electrical, optical, catalytic properties can then be affected by the control of the oxygen stoichiometry. In rf-sputtering technique, the bombardment energies on the substrate can be controlled by the deposition conditions leading to different oxygen stoichiometry in the growing layers. By this technique, thin films have been prepared from two ceramic targets: CuFeO 2 and CuO + CuFe 2 O 4 . We thus synthesized either Cu 0 /Cu x Fe 1− x O 4 nanocomposites thin films with various Cu 0 quantities or CuFeO 2 -based thin films. Two-probes conductivity measurements were permitted to comparatively evaluate the Cu 0 content, while optical microscopy evidenced a self-assembly phenomenon during thermal annealing.

International audience; Nanocomposites of metallic copper and iron oxides films have been prepared by RF-sputtering of pure CuFeO2 delafossite target. The films are made of copper and spinel ferrite crystallites of less than 10 nm in diameter. The content of metallic copper and the ferrite composition depend on the sputtering conditions. For the shortest substrate-target distances, films are made of copper and copper substituted magnetite with low copper content. The formation of the metallic and spinel phases is due to the loss of a small quantity of oxygen during sputtering. When annealed under inert atmosphere, nanometric copper particles located in the upper part of the film, move on the surface and grow due to coalescence phenomena. The particle motion can be stopped by small grooves allowing the self-assembly of copper particles.

Pure and rare earth ions doped yttrium oxide (Y2O3) waveguide films were prepared by a simple sol–gel process and dip-coating technique. Y2O3 were successfully synthesized by hydrolysis of yttrium acetate. The structural evolution of Y2O3 films with annealing temperature was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, waveguide Raman spectroscopy and High-resolution transmission electron microscopy. The propagation loss of Y2O3 thin films at 632.8 nm measured by scattering-detection method is approximately 1.5 dB/cm. The fluorescence of Er3+ and Eu3+ doped Y2O3 waveguide thin films were studied under the waveguide configuration. The fluorescence intensities evolution with annealing temperature of Y2O3:Er3+ films has been studied and was explained by the multi-phonon non-radiative processes. Our results show that Y2O3 is a good host material for optically active waveguide thin films and sol–gel process is a useful method to derive pure and doped Y2O3 waveguide films.

Room-temperature photoluminescence (PL) measurements were performed on erbium-doped AlN thin films deposited by r.f. reactive magnetron sputtering on steel and amorphous quartz substrates. The Al/(N+Al) ratio in the as-deposited films varies in the range from 0.48 to 0.51, while erbium content ranges from 0.2 to 3.5 at.%. X-ray diffraction showed that the AlN(Er) films with erbium contents up to 1.4 at.% have the hexagonal AlN crystalline structure and a preferential orientation following the [0 0 1] direction. However, as a consequence of lattice distortion and/or defect generation originated by the incorporation of erbium atoms in the AlN structure, the films became amorphous for higher erbium contents. All the as-deposited films exhibited room-temperature PL at 1.54 μm, indicating that at least part of the erbium species are optically active in the as-grown samples. Subsequent annealing of the films led to an intensification of the PL signal up to a factor of 6 for the films heat-treated at 1075 K. Within the range of chemical compositions studied in this work, the PL signal increased with increasing erbium content. A weak green visible PL was also detected for the samples doped with the highest erbium contents when annealed at high temperatures.

International audience; We discuss attractive potentialities of the sol–gel process applied to planar microcavities with distributed Bragg reflectors (DBRs). This method is well known for its good flexibility and the optical quality of the thin films obtained. The DBRs are composed of alternated TiO2 and SiO2 thin films. One of the main problems of the sol–gel process is the stresses induced during the layers heat treatment leading to defects and cracks in the films. The study of these stresses shows that with the appropriate annealing temperature and duration of the firing process, the stress in the SiO2 layers partially compensates the stress in the TiO2 layers. DBRs and microcavities formed by 60 stacked layers have been elaborated in these conditions. The reflectivity of such sol–gel DBRs reaches 99.7%. The sol–gel DBRs are used to fabricate microcavities containing Eu3+ rare earth ions with a quality factor of approximately 1000.

Thin films of lead titanate were prepared by a chemically modified sol-gel process and dip-coating technique. The process was refined such that homogeneous crack-free films could be produced which showed excellent waveguiding properties. A 600°C heat treatment was required to obtain the crystallization of the PbTiO3 perovskite phase. The microstructure of the phases was studied using waveguide Raman spectroscopy and transmission electron microscopy. The film was composed of an upper layer of large perovskite grains (∽100 nm) on a lower lead content phase which appeared at the layer/substrate interface. This microstructure was related to lead diffusion into the substrate during heat treatment as shown by Rutherford backscattering spectrometry.

The stress development in zirconium oxide gel films during annealing between 150 and 400°C has been investigated using thickness and substrate curvature measurements with laser beam reflections. The films' elemental content was determined by Rutherford backscattering spectrometry and their structure by X-ray diffraction. It is shown that the main densification mechanisms are polycondensation reactions up to 300°C with acetylacetone elimination leading to a rather weak stress increase. For temperatures above 300°C the vanishing of acetylacetone favors densification and stress increase.

We report on the preparation of SiO2 (20%)–TiO2 (80%) planar waveguiding layers by dip-coating technique. The layers are formed from originally prepared sol with the added CdO and the subsequent precipitation of CdS nanocrystals (NC) during H2S treatment. The initial sol doping up to 92 wt.% was reached. The determination of the refractive index and thickness of waveguiding layer by m-line spectroscopy is presented. The porosity of film is evaluated. Influence of carbon contamination of the layer's pre-surface area on the waveguiding properties is discussed. The possibilities of surface relief gratings as efficient input and output light couplers are demonstrated.

We report on the fabrication and the structural study of TiO2/Er3+ planar optical waveguides. The effects of erbium concentration and annealing temperature were first studied using the waveguide Raman spectroscopy technique. The later showed an important modification of the TiO2 host matrix induced by the presence of the Er3+ ions. Depending on their concentration, these ions seem to stabilize the TiO2 amorphous phase or limit the crystallization process. This result is confirmed by transmission electron microscopy (TEM) and X-ray diffraction.