One of the major challenges in environmental control is at present the monitoring of air and water quality as a prerequisite effectively controlling and counteracting pollution and enforcing new more stringent legislation. This requires highly selective, sensitive, fast, and low-costs sensors for efficient pollution monitoring. Many pollutants including hydrocarbons, oxides of nitrogen and sulphur generated through the combustion of fossil fuels, exhibit strong absorption lines in the Ultra-Violet (UV) spectral range which allows optical techniques to be used for rapid, sensitive and contactless gas sensing and monitoring exploiting this wavelength range. Spectroscopic optical sensing offers a range of significant advantages over other sensor concepts such as high selectivity and specificity, high sampling rate, real-time and on-line monitoring, as well as the capability of stand-off sensing and detection. Among the different available optical sensors, fiber coupled systems are most promising due to their compactness and robustness, inertness to chemical or electromagnetic interferences and multiplexing capabilities. In this project, we propose to develop a practical electrically-injected RC-LED emitting in the 380-400 nm range build on a epitaxially grown AlGaN/GaN DBR underneath an active GaInN/GaN MQW active region. The top DBR will be based on UV-transparent dielectric oxide layers. Specific variations in device design will allow to adjust the device emission wavelength to match the precise emission wavelengths for specific application, such as the absorption lines of the different polluting gases. The availability of such RC-LEDs coupled to an optical fiber for relaying the UV-light as well as for sensing will be of strong interest for spectroscopy community where European companies and research laboratories are strongly involved.

Le contact électrique entre deux conducteurs est essentiellement un problème d'interface. Dans le cas d'un connecteur, l'interface doit assurer non seulement une bonne continuité électrique, mais également une protection efficace contre la corrosion et le maintien d'un frottement faible. Parmi les dégradations liées aux conditions d'utilisation, citons par exemple celles résultant du microdéplacement des deux parties du contact sous l'effet de vibrations et/ou de variations de température. Ce phénomène est appelé fretting : c'est une des causes principales de défaillance des contacts électriques de connexion. La solution habituelle pour retarder ce phénomène est l'utilisation de lubrifiants liquides. Cependant en conditions extrêmes (ultravide, hautes températures, microsystèmes ...) le recours aux lubrifiants liquides classiques n'est pas possible. Dans ce contexte, la mise en œuvre d'une lubrification sèche représente un enjeu majeur. L'objectif de ce projet est d'élaborer un film conducteur d'épaisseur nanométrique capable de protéger son substrat de la corrosion tout en conservant un frottement faible et une usure minimum. Il s'agit ici de concilier des propriétés contradictoires puisqu'à ce jour la plupart des films anti-corrosion et anti-frottement sont mauvais conducteurs. Au-delà de cette innovation, cette étude devrait permettre d'avancer dans la compréhension des mécanismes de lubrification moléculaire. Notre méthodologie repose sur trois points forts. Dans un premier temps nous élaborerons des revêtements originaux associant des structures moléculaires semi-conductrices à des oligomères perfluorés greffés de façon covalente au matériau de contact (or, étain, cuivre), qui devront répondre aux exigences énoncées ci-dessus. Dans un deuxième temps, les propriétés conductrices et tribologiques (c'est-à-dire en frottement) de ces films organiques greffés d'épaisseur nanométrique seront étudiées, aux échelles macroscopique et microscopique. L'homogénéité de ces films est une condition essentielle d'obtention de propriétés macroscopiques satisfaisantes (faible frottement, bonne conduction). Elle ne peut être maîtrisée que par la compréhension et le contrôle des propriétés moléculaires. Les propriétés macroscopiques (électriques et mécaniques) seront étudiées à l'aide de bancs d'essais reproduisant des conditions réelles d'utilisation à partir de contacts sphère/plan modèles. Les propriétés microscopiques/nanométriques seront étudiées grâce à des techniques dérivées de la microscopie à force atomique: le troisième point fort concerne l'AFM à pointe conductrice, qui nous permettra d'obtenir des cartes de résistance et de friction locales. De plus le développement d'une extension « nano-fretting » sera entreprise de façon à simuler à l'échelle micro/nanoscopique le mécanisme de dégradation par fretting. Enfin, la protection des surfaces métalliques revêtues contre la corrosion sera évaluée sur la base des normes requises en connectique.

The production capacity of photovoltaics continues its amazing expansion, with an average yearly growth of 50% between 2001 and 2008. Keeping pace with this growth, large-area thin-film PV production has maintained its ~10% market share, but the technology that was expected to dominate the photovoltaic industry – thin film hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) tandem cells (the so-called “micromorph” design) – has not completely fulfilled its destiny. This due to a recent challenge by a simple, robust technology (CdTe) that has now grown to be the single largest thin film technology by production volume, and by slower than expected advancements in the stabilized efficiency of micromorph devices. Despite gradual and incremental improvements in thin film silicon technology, this PV module design continues to be limited by two factors: (1) a fundamental property of a-Si:H (its metastable light-induced degradation), and (2) the slow deposition rate of nc-Si:H. The proposed project aims to address these two limiting factors: firstly, by removing the primary barrier to stable thin-film silicon-based tandem cells by eliminating the troublesome a-Si:H and replacing it with a hydrogenated nanocrystalline silicon carbide alloy, and secondly, by depositing high-quality hydrogenated nanocrystalline silicon at a high deposition rate. The advantages of the micromorph tandem photovoltaic cell can be retained (high efficiency at low cost due to all silicon/carbon-based absorber layers), while opening new doors in terms of stabilized cell efficiency. The primary challenge to this Carbon Alloyed Nanocrystalline Silicon TAndem (CANASTA) design is obtaining absorber layer quality nanocrystalline silicon carbon (nc-SiC:H) at low temperatures (<300°C). This challenge will be addressed using novel deposition techniques with new levels of precursor flux control. To achieve the widest range of freedom in processing conditions, three novel deposition strategies will be investigated for this challenging material to learn the most about the specific physical processes required to produce high quality material. One of these techniques (for which a patent is currently being filed by the LPP and LPICM), the use of novel excitation voltage waveforms, will also be applied to the challenge of high deposition rate nc-Si:H, the second crucial component of the CANASTA design. The other technique will include the use of high-density microwave excited PECVD and the use of novel precursor gases. In addition, the project addresses a major barrier to the development of new thin-film photovoltaic materials – the lack of a foolproof intrinsic layer characterization method that accurately predicts out-of-plane electronic transport properties, as most thin-film characterization methods probe the in-plane transport properties and can give misleading optimization guidelines. The project will additionally address this problem by developing two advanced characterization techniques for thin-films, namely the spectroscopic surface photovoltage and wavelength dependent steady state photocarrier grating techniques – and applying these techniques to intrinsic nc-Si:H and nc-SiC:H thin films in the optimization process.

Cooperative communication can be applied to both infrastructure-based networks, such as cellular systems, WLANs (wireless local area networks), WMANs (wireless metropolitan area networks), and infrastructure-less networks, such as MANETs (mobile ad hoc networks), VANETs (vehicular ad hoc networks), and WSNs (wireless sensor networks). With large existing target markets and indisputable advantages, cooperative communication is one of the best opportunities today for high impact research in the area of wireless communications. As such, this emerging research area has spurred tremendous excitement within the academia and industry circles and resulted in a surge of research papers over the last few years. In order to cater for the increasing demand for higher data rate and robustness, a new form of cellular network architecture has emerged recently as a subject of great interest described by a variety of problems: • Denser and denser deployment with low, aggressive frequency reuse factor is required. • Multiple-antenna (Multiple-Input Multiple-Output, MIMO) transmission techniques are used to provide high capacity and robust links. • Multiple-user communication is about to be developed to exploit the available spatial degrees of freedom in an efficient manner, especially with the introduction of MIMO technology. • Relay-aided systems will become a reality as a means to improve network coverage, data reliability, and ultimately user satisfaction. The convergence of these developments appears to have huge potential to boost the network throughput to a whole new level. Meanwhile, the challenging problems of inter-cell interference and indoor coverage, when all users share the same frequency band, do remain and will become the main barriers to higher data rates. The possibility of exploiting relay stations to reinforce signal and to mitigate interference, as well as that of revealing new modes of relay communication, opens up a wide array of research problems. Clearly, this involves all the problems encountered in cellular networks plus many more. Although abundant amount of information-theoretic results on relay-aided communications exist, translating the promises of these results into practical engineering solutions has remained extremely challenging. The most significant obstacles to overcome are • To understand the fundamental information-theoretic limits of multiuser relay-aided communication for realistic systems; • To develop efficient codes and strategies with reasonable complexity from a practical point of view; • To jointly design the physical (PHY) and medium access control (MAC) layers in order to optimize the overall performance and to integrate into existing infrastructure in a meaningful way. Since these three problems are intertwined, there is a need for a truly multi-disciplinary and comprehensive approach to relay-aided communication, which would draw on the theoretical analysis of practically relevant information-theoretic wireless models to guide the design of efficient coding schemes and relaying strategies. This project brings together two teams expert in the domain, with established European and international recognition: Supélec (SUP), France and Peking University (PKU), China. The teams have complementary areas of expertise that encompass information theory, coding theory, wireless communications and networking, and cross-layer optimization, which all are particularly relevant for the project. Obtaining significant support is of primal importance as it will allow both teams to attract talented students and post-docs and to reinforce their position at the forefront of this domain.