Impression de silicium par procédé jet d'encre (des nanoparticules aux couches minces fonctionnelles pour applications photovoltaïques)

Cette étude prend place dans le cadre du projet ANR Inxilicium visant à la réalisation de cellules solaires en couches minces de silicium par jet d encre. Les nanoparticules de silicium sont des matériaux à fort potentiel pour la levée de verrous technologiques grâce à leurs propriétés spécifiques. Des encres de nanoparticules de Si issues de diverses méthodes de synthèse ont été imprimées par jet d encre sur différents substrats : quartz, électrodes métalliques (aluminium, molybdène) et transparente conductrice (ZnO:Al). L optimisation du procédé d impression, de l interaction encre/substrat (via la modulation de l énergie de surface des substrats) et de l étape de séchage a permis l obtention de couches minces homogènes et continues (plusieurs centaines de nm à quelques m d épaisseur)A posteriori, une étape de recuit est nécessaire pour recouvrer des propriétés fonctionnelles. L utilisation de nanoparticules à la physico-chimie de surface contrôlée fait décroître les températures de frittage de 1100 C à environ 600 C. En complément, des recuits sélectifs (micro-ondes et photonique) ont été évalués pour leur application sur des substrats flexibles et bas coûts.Les propriétés optiques et les interfaces électrode/silicium ont été examinées afin d intégrer ces couches dans des dispositifs (cellule solaire ). La formation de transitions métallurgiques Al-Si et Mo-Si a été étudiées par DRX-in situ. L ensemble de ces travaux a permis la réalisation d une jonction PN montrant un comportement photovoltaïque à fort champ grâce aussi à la mise au point d une méthode innovante de collage ouvrant la voie à une réduction du bilan thermique des procédés de fabrication.This study takes place in the frame of the Inxilicium project from the National Research Agency, which targets the fabrication of silicon thin film solar cells by inkjet-printing. Thanks to their specific properties, silicon nanoparticles are materials with strong potential for technological breakthroughs. Silicon nanoparticle-based inks made by different synthesis routes have been inkjet-printed on different substrates: quartz, metallic electrodes (aluminum, molybdenum) and transparent electrodes (ZnO:Al). Homogeneous and continuous thin films (from several hundreds of nm to some m thick) have been obtained through optimization of the printing process, the ink/substrate interaction (via substrates surface energy tuning) and the drying step.A posteriori, an annealing step is mandatory for recovering of functional properties. By using nanoparticles with tailored surface physical chemistry, the sintering temperature decreases from 1100 C to 600 C. In order to allow the use of this material on flexible and low cost substrates, selective sintering (microwave and photonics) have been also evaluated.Thin film optical properties and electrode/silicon interfaces have been investigated with the purpose to integrate those layers into devices (solar cells ). Metallurgical evolution of Al-Si and Mo-Si physical interfaces has been studied by in situ XRD.This work allowed the fabrication of a PN junction with a photovoltaic behaviour under strong polarization voltage thanks to the development of an innovative thermal pasting process, which opens the way to the reduction of process thermal budget.ST ETIENNE-ENS des Mines (422182304) / SudocGARDANNE-Centre microélec. (130412301) / SudocSudocFranceF

Fabrication of Capacitive Acoustic Resonators Combining 3D Printing and 2D Inkjet Printing Techniques

International audienceA capacitive acoustic resonator developed by combining three-dimensional (3D) printing and two-dimensional (2D) printed electronics technique is described. During this work, a patterned bottom structure with rigid backplate and cavity is fabricated directly by a 3D printing method, and then a direct write inkjet printing technique has been employed to print a silver conductive layer. A novel approach has been used to fabricate a diaphragm for the acoustic sensor as well, where the conductive layer is inkjet-printed on a pre-stressed thin organic film. After assembly, the resulting structure contains an electrically conductive diaphragm positioned at a distance from a fixed bottom electrode separated by a spacer. Measurements confirm that the transducer acts as capacitor. The deflection of the diaphragm in response to the incident acoustic single was observed by a laser Doppler vibrometer and the corresponding change of capacitance has been calculated, which is then compared with the numerical result. Observation confirms that the device performs as a resonator and provides adequate sensitivity and selectivity at its resonance frequency

Results from prototypes of environmental and health alarm devices based on gaseous detectors operating in air in counting mode

International audienceWe have developed and successfully tested two prototypes of detectors of dangerous gases based on wire-type counters operating in air in avalanche mode: one is for radon (Rn) detection whereas the other one is for the detection of gases with an ionization potential less than the air components. Due to the operation in pulse counting mode these prototypes have sensitivities comparable to (in the case of the Rn detector) or much higher than (in the case of the detector for low ionization gases) the best commercial devices currently available on the market. We believe that due to their high sensitivity, simplicity and low cost such new detectors will find massive applications. One of them, discussed in this paper, could be the on-line monitoring of Rn for the prediction of earthquakes

Characterization of organic ultra-thin film adhesion on flexible substrate using scratch test technique

International audienceThe mechanical properties of interfaces and more precisely the adhesion are of great importance for the understanding of the reliability of thin film devices. Organic thin film transistors (OTFT) on flexible substrate are a new class of electronic components. Since these devices are flexible and intended for different fields of application like sensors and displays, they will undergo a lot of mechanical and thermal stress during their useful life. Moreover, interfaces play an important role in the electrical stability of these transistors. In this context, the adhesion of two organic submicron thin films, semi conducting and dielectric respectively, deposited on polymeric substrate were investigated by scratch test method. This study demonstrates the feasibility and selectivity of the scratch test as a tool for assessing the adhesion and the damage behaviour of ultra-thin organic film on flexible plastic substrate. The semi-crystalline substrate presents a brittle cracking damage from a given strain, whereas when covered by the semi-conducting thin film, the sample exhibits a more ductile behaviour. Moreover, this technique has proven to be sensitive enough to highlight the effects of a plasma treatment prior to deposition

Organic ultrathin film adhesion on compliant substrate using scratch test technique

International audienceMany adhesion test techniques have been developed to measure the adhesion energy of thin films but they are hard to implement in the case of submicron organic thin films deposited on a flexible substrate. Recently the feasibility and repeatability of the scratch test technique as a tool for testing the adhesion and the damage behaviour of ultra-thin films on polymer substrates has been demonstrated. However, direct comparison of the critical load between samples was not straightforward since different failure mechanisms were induced. In the present work, we have performed nanoscratch experiments on submicron thin films deposited on a flexible substrate. The use of a tip radius of 5 μm enabled a unique delamination mechanism to be induced by localizing and maximizing the stress closer to the interface. We have observed an increase of the critical load on samples processed with an adhesive plasma treatment prior to thin film deposition, confirming the effectiveness of this treatment. We have also performed mechanical ageing tests on specimens and proved that the scratch test technique is sensitive enough to monitor the degradation of the interface properties. Finally, we have discussed some existing energy models. Taking into account some limitations, Laugier's model gives an upper bound for the adhesion energy

Le chromage dur : l'apport du chrome trivalent

National audienc

An overview of hard chromium plating using trivalent chromium solutions

http://www.pfonline.com/articles/an-overview-of-hard-chromium-plating-using-trivalent-chromium-solutionsInternational audienc

Les liquides ioniques : une nouvelle donne pour les traitements de surface.

National audienc

Les Liquides Ioniques : une nouvelle donne pour les traitements de surface ?

Publication à paraîtreNational audienc

Elaboration électrochimique, caractérisation et compréhension des mécanismes de formation des films d'oxyde d'aluminium nano-poreux organisés

La structure théorique des membranes nanoporeuses et ordonnées d alumine est semblable à une structure en nid d abeille qui est obtenue uniquement pour des paramètres d anodisation bien spécifiques. Plusieurs modèles ont été proposés pour expliquer la formation des structures ordonnées, mais il reste quelques zones d ombre. Cette étude se propose d apporter des compléments aux études déjà réalisées sur l influence des paramètres agissant sur la géométrie de l alumine et d améliorer la compréhension des phénomènes intervenant lors de la formation de ces structures. En particulier, nous proposons une approche originale basée sur la migration des anions dans la couche barrière qui permet d expliquer pourquoi la structure idéale n est obtenue que pour une gamme restreinte de différence de potentiel anode/cathode qui diffère selon l électrolyte utilisé. Elle apporte ainsi un éclairage nouveau sur le processus d anodisation ordonnée en termes de différences de potentiel.The theoretical structure of highly ordered nanoporous alumina membranes is similar to a honey-comb. However, the ideal structure consisting of a regular cells network is obtained only for very specific anodizing parameters. Several models have been proposed, whereas they are not sufficient to explain entirely the formation of theses structures. In this study, we propose to complete the literature on the influence of various parameters which play a role on the structure of the highly ordered nanoporous alumina and to improve understanding of phenomena involved in the formation of these structures. In particular, we propose an original approach based on anions migration in the barrier layer which permits to explain why anodic oxidation of aluminium leads to ordered structures only for a restricted range of cell voltage which depends on the electrolyte used. Thus, this study brings a new point of view on the process of formation of highly ordered nanoporous alumina in terms of voltage.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF