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The paper investigates the formation of thin porous amorphous silicon carbide (PASiC) by Al-assisted photochemical etching using HF/AgNO3 solution under UV illumination at ? = 254 nm. Different etching times varying from 2 to 10 min have been used on thin a-Si0.60C0.40:H films, which are elaborated by co-sputtering DC magnetron using a single crystal Si target and who deposited onto 86 of hot pressed polycrystalline 6H-SiC stripes of 12.5 mm3. Because of the high electrical resistivity of the thin a-Si0.60C0.40:H film higher than 2 MΩ cm, and in order to facilitate the chemical etching, a thin metallic film of high purity aluminum (Al) has been deposited under vacuum, follow-up of a thin palladium deposited under a grid to reduce attacked surface and reinforced solution etching. The etched surface was characterized by scanning electron microscopy, infrared spectroscopy, spectrophotometer UV, and photoluminescence. Results show that the morphology of etched a-Si0.60C0.40:H surface evaluates with etching time and presents a spongy and macroporous layers. Where, the diameter of pore size increases with the increasing etching time. A humidity sensors were fabricated through evaporating coplanar interdigital gold electrodes on PASiC and the humidity sensing properties were tested, it show, that the measured resistance Au-PASiC structure, depends highly on the applied bias voltage. Finally, the sensing performances are attributed to the unique surface structure, morphology of the pore and its size, that provide an effective pathway for vapor transportation and enlarged the sensing area of Au-PASiC.

We have determined the single phase domain of LiGd 1− x Yb x (WO 4 ) 2 . The lattices parameters decrease as a function of Yb 3+ substitution in Gd 3+ sites. Transparent LiGd 1− x Yb x (WO 4 ) 2 fibers single crystals were successfully grown by the micro-pulling down technique (μ-PD). The Yb 3+ -doped LiGd(WO 4 ) 2 fibers single crystals have been pulled under stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to 120 μm. The fibers diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Fibers single crystals free of defects are observed for Ytterbium concentration in the melt up to 5 at%. Above this limit, inclusions and cracks appear and the optical quality of the fibers were deteriorated. The emission spectra of Yb 3+ -doped LiGd(WO 4 ) 2 were investigated.

Thin films of InSe were obtained by thermal and flash evaporation techniques on glass substrates maintained at various temperatures ( T S =30, 100, 160, 200°C). The best films were obtained for a substrate temperature of 160°C followed by annealing at 200°C for 6 h. Analysis of the films showed strong decomposition of films obtained by thermal evaporation. Structural studies showed the presence of In 4 Se 3 with InSe. The chemical formula of the composite is In x Se 1− x . The values of x found by the microprobe analysis vary between 0.52 and 0.56. Optical absorption data are also explained in terms of composition variation.

International audience; In this paper, we present the results of our attempt to grow NaBiW2O8 (NBW) and Na5B2P3O13 (NBP) crystals by the heat exchanger method (HEM). This method is slightly different from the Bridgman technique: the crucible is kept fixed in the setup and the center of the crucible bottom is cooled by a variable helium gas flow. It allows very good control of the growth rate and minimizes parasitic crystallization at the crucible walls. First experiments for growing these two materials by the HEM technique have shown very promising results with single-crystal sizes of few cubic centimetres..

In this work a developed experimental setup for the direct laser writing (DLW) system of a photolithography mask for integrated photonics devices will be described. The DLW system is mainly composed of a pulsed Nd:YAG laser source, beam handling system, (X-Y) table, PC computer, CCD camera and TV monitor. The synchronization between the laser source and the (X-Y) table is achieved by a NI Instruments and LabVIEW based program. The experimental micromachining results from some samples of continuous writing lines obtained by removal of chromium deposited on glass substrates will be presented and discussed.

International audience; Crystal growth and spectroscopic study of the new compound Yb3+:LiLu(WO4)2 have been undertaken for the first time. Preliminary growth using flux method with Li2W2O7 as solvent allows us to obtain small single crystals. As a promising laser crystal, Yb3+:LiLu(WO4)2 have characteristics of a low concentration quenching effect and low laser threshold owing to the existence of covalent bands in WO4 group. Its absorption peak at 977 nm, corresponding to 2F7/2(1) → 2F5/2(5) transition, is suitable for laser diode pumping. Emission spectrum shows large bands extending from 900 to 1100 nm, five peaks centred respectively at 959, 978, 997, 1025 and 1056 nm are well resolved. The FWHM of the most intense emission band located at 997 nm is about 20 nm. Energy Stark levels are: 0, 201, 469 and 749 cm−1 for the 2F7/2 component and: 10,230, 10,427 and 10,890 cm−1 for the 2F5/2 component. The overall splitting of 2F7/2 ground-state manifold is 749 cm−1, which is larger than that observed in similar systems such as Yb3+:LiLa(WO4)2 (632 cm−1). Such large crystal-field splitting of the 2F7/2 ground-state will be advantageous to lower laser thermal effect and re-absorption losses. As we can see, the stark electronic levels are characterized by relatively large crystal-field splitting favourable to laser crystal applications in the near infrared spectral region.

International audience; X-band electron spin resonance (ESR) spectra and fluorescence measurements were performed on Mn-doped Na2ZnP2O7 (NZPO) single crystal synthesized by the Czochralski pulling method and glasses synthesized by the quenching process. For the single crystal, ESR angular dependences were measured in both the zx and xy plans of the NZPO lattice. The fine and hyperfine structure parameters and g-factor values were determined by modelling the experimental spectra. Using the Newman superposition model, the resonating centres in the single crystal and powder (crushed from crystals) samples are assigned to Mn2+ ions substituting for both zinc and sodium. For the glass sample the analysis of the ESR data shows that Mn2+ ions substitute for the Na+ ions. These interpretations are confirmed by the fluorescence measurements with a unique broad red band for the glassy compound and the presence of two emission bands (green and red) in the case of the crystal sample.

In this paper, we present the design of a low cost Q‐switched Nd: YAG laser micro‐machining system for photo masks fabrication. It consists of: Nd:YAG laser source, beam delivery system, X‐Y table, PC, The CCD camera and TV monitor. The synchronization between the laser source and the X‐Y table is realised by NI PCI‐7342, the two axis MID‐7602 and LabVIEW based program. The first step of this work consists of engraving continuous and discontinuous lines on a thin film metal with a 100 μm resolution by using the YG 980 Quantel Q‐switched Nd:YAG laser.

A tractable model of the tail-state distribution in alloys is obtained by minimizing the entropy of composition fluctuation in an assumed spherical well. This model is used to analyse the photoluminescence band due to recombination of localized excitons in Zn-rich ZnHgTe and Cd-rich CdHgTe.