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Abstract

The development reported herein is that of a surface micromachining technology using two SU-8 layers as a structural material. Three different processes are presented and discussed: the first process makes use of a solgel as the sacrificial layer; the second process utilizes the SU-8 itself as the sacrificial layer; the third process utilizes silicon dioxide as the first sacrificial layer and the solgel as the second sacrificial layer. These three processes are adapted for one structural layer structure. With a two-layer structure and when release is long, the third process is more adapted.

Résumé

Nous étudions l'amélioration des propriétés électriques des VCSELs (Vertical Cavity Surface Emitting Laser) de grande dimension (100um) à injection metallique annulaire pour application à la génération de puissance et pour la manipulation de solitons de cavité. Une simulation électrique nous a permis de quantifier l'amélioration de l'uniformité d'injection des porteurs apportée par les solutions technologiques que nous proposons de réaliser: l'adjonction d'une couche conductrice d'ITO à la surface du miroir supérieur du laser est ici évaluée.

Abstract

Nano energetic materials (nEMs) offer the promise of much higher energy densities, faster rate of energy release, greater stability and more security and could therefore give response to micro energetics challenges. In that context, nano thermite composites, also termed as Metastable Intermolecular Composites (MIC), have become one intensive research focus. In MIC, oxidizer and fuel are mixed at nano scale, thus leading to the improved performance in terms of energy release, sensitivity, stability, and mechanical properties compared to their bulk or micro counterparts. In the literature, there are different approaches to realize MIC such as physical mixing of nano powders of fuel and oxidizer, employment of sol-gel chemistry, deposition of multi-layer nanofoils of oxidizer and fuel, and embedding an array of Fe2O3 nanowires inside a thin Al film. In this study, we propose a novel approach of synthesis of Al/CuO MIC that is completely compatible with MEMS. We successfully develop large-area, uniform, and vertically aligned pure CuO nanowires (<50nm in diameter) by thermal annealing copper thin film deposited onto silicon substrate. Then nano Al is integrated within the CuO nanowires networks to realize a fascinating Al/CuO based MIC. The experimental processes will be first presented. Then different parameters 277 that affect the growth of CuO nanowires are studied in detail. The realized nanowires are then characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). Our approach has several advantages compared to previous investigations. First, Al/CuO MIC is realized by integrating nano Al with CuO nanowires grown from copper thin film, thus enhancing the interfacial contact area, atomic mixing and reactivity compared to powders. Second, the presence of impurities and Al oxidation are much smaller than that in sol-gel or powder mixing processes because the MIC is fabricated under vacuum. Third, since the dimensions of CuO nanowires can be tailored by adjusting the annealing conditions (temperature, duration, gas flow, etc.), the oxidizer/fuel dimensions can be controlled at nanoscale. Fourth, the homogeneity of the final MIC material is improved because only CuO (not Cu2O). Fifth, basically, the fabrication process is simple and can be integrated into a MEMS process. This will result in potential nano based functional structures, for example, nano energetic material based high performance igniter.

Abstract

Future adaptive optics (AO) systems require deformable mirrors with very challenging parameters, up to 250 000 actuators and inter-actuator spacing around 500 &mgr;m. MOEMS-based devices are promising for the development of a complete generation of new deformable mirrors. Our micro-deformable mirror (MDM) is based on an array of electrostatic actuators with attachments to a continuous mirror on top. The originality of our approach lies in the elaboration of layers made of polymer materials. Mirror layers and active actuators have been demonstrated. Based on the design of this actuator and our polymer process, realization of a complete polymer-MDM has been done using two process flows: the first involves exclusively polymer materials while the second uses SU8 polymer for structural layers and SiO2 and sol-gel for sacrificial layers. The latest shows a better capability in order to produce completely released structures. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then, we have developed a dedicated 14-bit electronics in order to "linearize" the actuation, using a calibration and a sixth-order polynomial fitting strategy. The response is nearly perfect over our 3×3 MDM prototype with a standard deviation of 3.5 nm; the influence function of the central actuator has been measured. First evaluation on the cross non-linarities has also been studied on OKO mirror and a simple look-up table is sufficient for determining the location of each actuator whatever the locations of the neighbor actuators. Electrostatic MDM are particularly well suited for open-loop AO applications.

Mots-Clés / Keywords

Abstract

Germanium material is particularly suitable for high frequency applications, especially RF MEMS ones. It may be used not only as sacrificial layers, like previously published in the literature, but also into the elaboration of integrated resistors for serial RF MEMS switches. The compatibility of germanium as resistive material in MEMS has been carried out and led to the successful demonstration of integrated Ge resistors into serial RF MEMS variable capacitors, without any RF perturbations. The compatibility of this layer with the MEMS process has been studied and validated with variable MEMS capacitors employed as demonstrators.