Design and Modeling of Micromechanical GaAs based Hot Plate for Gas Sensors

For modern Gas sensors, high sensitivity and low power are expected. This paper discusses design, simulation and fabrication of new Micromachined Thermal Converters (MTCs) based on GaAs developed for Gas sensors. Metal oxide gas sensors generally work in high temperature mode that is required for chemical reactions to be performed between molecules of the specified gas and the surface of sensing material. There is a low power consumption required to obtain the operation temperatures in the range of 200 to 500 oC. High thermal isolation of these devices solves consumption problem and can be made by designing of free standing micromechanical hot plates. Mechanical stability and a fast thermal response are especially significant parameters that can not be neglected. These characteristics can be achieved with new concept of GaAs thermal converter.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Preparation of nickel, nickel-iron, and silver-copper nanoparticles in ionic liquids

Room temperature ionic liquids (RTILs) are unique in many respects. The preparation method reported here is based on their extremely low vapour pressure that allows for their usage in vacuum. By magnetron sputtering of nickel or by co-sputtering of Ni-Fe or Ag-Cu on a surface of several imidazolium-based RTILs, we prepared nanocolloids containing metallic nanoparticles ranging in size from 6 to 30 nm, depending on the kind of RTIL, with low size dispersion. The nanocolloids are stable in time, no sedimentation or agglomeration was observed after two years. The method can be used also for preparation of the nanoparticles from semiconducting or insulating materials. As the next step, nanocolloids prepared in this way can be used for decoration of thin-film gas sensors by proper nanoparticles aiming at enhancement of their sensitivity and selectivity. Two ways of immobilization are presented mild heating of a drop of colloid containing Ni-Fe nanoparticles placed on TEM mesh, and Ag-Cu nanoparticles that were immobilized on the surface of gold thin-film electrode by electrophoresis

Quantification of hydrogen isotopes by CF-LIBS in a W-based material (WZr) at atmospheric pressure: from ns towards ps

Tungsten-based materials are possible candidates as PFCs in future fusion devices. LIBS is one of the most suitable techniques for monitoring erosion and deposition processes including fuel retention, due to its versatility and ability to perform in situ measurements. By deploying ps-LIBS, instead of ns, the laser ablation occurs with fewer melting effects. This work compares ns- and ps-(CF)-LIBS characterization of WZr(D) samples, at the linear plasma generator at Magnum-PSI at the DIFFER. The laser energy has been optimized for both laser regimes, lowering the laser energy for the ns regime (from 19.9 mJ pulse−1 to 7.4 mJ pulse−1) to approximate to ps regime (0.3 mJ pulse−1). All the experimental measurements have been performed at Patm. The pure WZr samples have been analyzed in ambient air, while the WZrD sample measurements have been performed under Ar gas flow. The retained deuterium content varies from 4 at% to 0.3 at%

Quantification of hydrogen isotopes by CF-LIBS in a W-based material (WZr) at atmospheric pressure: from ns towards ps

Tungsten-based materials are possible candidates as PFCs in future fusion devices. LIBS is one of the most suitable techniques for monitoring erosion and deposition processes including fuel retention, due to its versatility and ability to perform in situ measurements. By deploying ps-LIBS, instead of ns, the laser ablation occurs with fewer melting effects. This work compares ns- and ps-(CF)-LIBS characterization of WZr(D) samples, at the linear plasma generator at Magnum-PSI at the DIFFER. The laser energy has been optimized for both laser regimes, lowering the laser energy for the ns regime (from 19.9 mJ pulse−1 to 7.4 mJ pulse−1) to approximate to ps regime (0.3 mJ pulse−1). All the experimental measurements have been performed at Patm. The pure WZr samples have been analyzed in ambient air, while the WZrD sample measurements have been performed under Ar gas flow. The retained deuterium content varies from 4 at% to 0.3 at%

Influence of passivation-induced stress on the performance of AlGaN/GaN HEMTs

This paper reports on properties of intentionally undoped AlGaN/GaN/sapphire-based high electron mobility transistors (HEMTs) before and after passivation with SiO2 and Si3N4. Our results indicate that the DC performance of the AlGaN/GaN HEMTs improved significantly as the stress in the passivation layer increased from compressive to tensile. It corresponded to changes in the sheet carrier concentration. Unlike the DC properties, RF properties of the HEMTs were less sensitive to the stress

Mechanical, geometrical, and electrical characterization of silicon membranes for open stencil masks

Silicon membranes are used for stencil masks which are key to charged particle projection lithography, particularly for ion projection lithography, electron beam projection. Quantitative and qualitative determination of the mechanical properties of the true thickness, thickness variations (morphology), electrical conductivity and stress is critical to the development of next generation lithography. The metrology setup includes high accuracy thickness, refractive index and electrical conductivity measurement based on infrared variable angle spectroscopic ellipsometry, thickness variation characterization based on the Fizeau interferometric scheme and mechanical stress evaluation based on a novel double bulging technique