Publications

2013

• Applications de la spectroscopie Raman et photoluminescence polarimétriques à la caractérisation des contraintes dans les structures semi-conductrices à base de silicium, germanium et d'arséniure de gallium
  
  • Ndong Gerald
  , 2013. De nos jours, l'augmentation des performances et la réduction des dimensions des composants microélectroniques ou optiques constituant les systèmes électroniques ou optroniques nécessite des techniques de caractérisation non destructrices, capables de sonder des micro- et nanoobjets. C'est dans cette optique que s'inscrivent les techniques de spectroscopie Raman et photoluminescence, capables de caractériser localement les contraintes mécaniques, introduites dans les dispositifs à semi-conducteurs actuels afin d'accroître leurs performances. Ce travail de thèse aborde deux objectifs, l'élargissement des capacités du spectromètre Raman polarimétrique comprenant l'ajout d'un module de détection du signal de luminescence et l'application des techniques et méthodologies développées à la caractérisation des contraintes dans des structures semiconductrices à base de silicium, germanium et arséniure de gallium. Après une étude expérimentale des paramètres pertinents, la dépolarisation, le retard et le dichroïsme, nécessaire afin de combiner le spectromètre Raman " classique " et un polarimètre, nous avons montré que l'étalonnage d'un tel système dépend de la longueur d'onde de la source d'excitation, ainsi que de la nature de la diffusion considérée (Raman ou Rayleigh). Au titre des applications de la technique, nous avons mesuré des contraintes mécaniques dans des nanolignes de silicium (15 nm d'épaisseur) et des microlignes de germanium grâce à la méthodologie de mesure développée. Les résultats obtenus ont été également modélisés analytiquement afin de mettre en évidence la physique des phénomènes observés. Ainsi, nous avons montré qu'il est possible d'amplifier le signal Raman dans les nanolignes de silicium grâce à la gestion appropriée des polarisations des rayonnements incident et diffusé. La mise en place de la technique de photoluminescence avec le contrôle des états de polarisation, rajoutée à la spectroscopie Raman, nous a permis d'étendre le champ de mesure des contraintes mécaniques dans les structures semiconductrices. Actuellement, grâce à cette technique, nous sommes capables de mesurer des efforts résiduels de l'ordre de 20 MPa, ce qui est au-delà des capacités de la spectroscopie Raman " conventionnelle " essentiellement limitée par la résolution spectrale.
• Microscopic measurements of variations in local (photo)electronic properties in nanostructured solar cells
  
  • Fejfar Antonin
  • Hyvl Matej
  • Ledinsky Martin
  • Vetushka Aliaksei
  • Stuchlik Jiri
  • Kocka Jan
  • Misra Soumyadeep
  • O’donnell Benedict
  • Foldyna Martin
  • Yu Linwei
  • Roca I Cabarrocas Pere
  Solar Energy Materials and Solar Cells, Elsevier, 2013, 119, pp.228. (10.1016/j.solmat.2013.07.042)
  DOI : 10.1016/j.solmat.2013.07.042
• Nanostructured hybrid solar cells based on PECVD grown SiNWs and organic semiconducting polymers
  
  • Jeon Taewoo
  , 2013. Solar cells are an exciting alternative energy technology due to the infinite energy source, the Sun. Many types of solar cells based on inorganic or organic materials are currently developed with the objective of higher efficiency and lower cost. In this context, this thesis suggests to study nano-structured hybrid solar cells based on silicon nanowires (SiNWs) and organic active materials to benefit advantages of both materials. SiNWs are grown by PECVD on transparent conducting oxide via Vapor-Liquid-Solid (VLS) mechanism with careful control of their nano-morphology. The organic materials made of polymers or blend polymers are then deposited by spin-coating on top of SiNWs. In these hybrid solar cells the SiNWs are used as light-trapping medium and/or electron acceptor material. For better solar cell performance, the optimization of SiNWs array is carried out by removing residual catalyst and etching parasitic hydrogenated amorphous silicon. Their effects on hybrid solar cells have been fully analyzed and discussed. Furthermore, the electron-acceptor properties of the nano-structured SiNWs have been estimated with Bismuth-doped n-type SiNWs. The results clearly reveal the potential of this type of hybrid solar cells, namely, 1) power conversion efficiency improvement by enhancing external quantum efficiency in longer wavelength regime and 2) variety uses of SiNWs by tuning their electrical property and morphology.
• Imagerie polarimétrique pour le diagnostic de néoplasies intra épithélialesdu col utérin : étude de conisations et de lames histologiques de tissus conjonctifs
  
  • Nazac André
  , 2013. Etant sensible à la polarisation de la lumière et non à son intensité, l'imagerie polarimétrique peut révéler des propriétés de l'objet étudié invisibles en imagerie classique. Cette technique présente un réel potentiel pour le développement de nouveaux diagnostics optiques dans le domaine médical. L'imagerie polarimétrique est particulièrement performante pour détecter les modifications de la structure du collagène fibrillaire dans les tissus conjonctifs, modifications qui accompagnent (ou précèdent) l'apparition de nombreuses pathologies, parmi lesquelles le cancer du col utérin et le prolapsus vaginal. Ce travail a porté essentiellement sur l'étude, en microscopie polarimétrique, de la structure du collagène dans des lames histologiques issues de conisations (cols utérins extraits pour suspicion d'états précancéreux) et de prélèvements de parois vaginales, pour corréler cette structure avec la présence ou l'absence de pathologie. Après une brève introduction, le premier chapitre décrit la prise en charge actuelle du cancer du col utérin, son efficacité et aussi ses limites, qui justifient pleinement la recherche d'une nouvelle technique de diagnostic optique de cette pathologie. Le chapitre suivant est consacré au prolapsus génital, pour lequel une détection précoce des personnes à risque serait également très bénéfique. Le troisième chapitre décrit succinctement la polarisation de la lumière. Le chapitre suivant est consacré aux matériels et méthodes mis en {\oe}uvre, des polarimètres imageurs à la préparation des échantillons. Les résultats sont résumés dans les deux derniers chapitres. Dans le tissu vaginal normal le collagène est orienté différemment dans les trois couches principales (muqueuse, musculeuse et adventice), alors que cette structure disparaît dans du tissu prolabé. Sur les cols utérins, nous avons mis en évidence la présence, juste sous l'épithélium malphighien, d'une couche de collagène orienté parallèlement à l'éptihélium et dont la biréfringence est bien plus importante dans les zones saines que sous des dysplasies. Cette couche pourrait être la principale responsable des contrastes polarimétriques observées en rétrodiffusion sur des cols épais avec une biréfringence et une dépolarisation plus fortes dans les zones saines que dans les zones dysplasiques.
• Procédé de dépôt de nanoparticules sur un substrat d'oxyde métallique nanostructure
  
  • Aldakov Dmitry
  • Ivanova-Hristova Valentina
  • Reiss Peter
  • Sanchez Sylvia
  , 2013.
• Using nanowires to enhance light trapping in solar cells
  
  • Foldyna Martin
  • Yu Linwei
  • Misra Soumyadeep
  • Roca I Cabarrocas Pere Roca I Cabarrocas
  SPIE Newsroom, Spie, 2013, pp.1. (10.1117/2.1201311.005205)
  DOI : 10.1117/2.1201311.005205
• Improving the performance of polymer light-emitting devices with chemical tools
  
  • Zucchi Gaël
  • Tondelier Denis
  • Bonnassieux Yvan
  • Geffroy Bernard
  Polymer international, Wiley, 2013, 63 (8), pp.1368 - 1377. This review presents the strategies that have been employed to build polymer light‐emitting devices as far as the chemical design of fully conjugated polymers and device structure engineering are concerned. In particular, it gives an overview of the wealth of materials used as single emissive layers imagined by chemists in the quest for the improvement of the efficiency of devices with simplified structures. We give selected examples of the efforts made to synthesize materials that can transport both positive and negative charge carriers. The last part is devoted to the attention paid to highly emissive materials with a special focus on single conjugated electro‐phosphorescent polymers. (10.1002/pi.4638)
  DOI : 10.1002/pi.4638
• About the step-flow mechanism at the origin of graphene crystallisation at the surface of catalysts
  
  • Maurice Jean-Luc
  • Pribat Didier
  • He Zhanbing
  • Patriarche Gilles
  • Cojocaru Costel Sorin
  , 2013. The nucleation and growth of multiwall carbon nanotubes (MWCNTs) at the surface of crystalline iron-based catalysts are studied by in situ annealing and high-resolution transmission electron microscopy. Graphene planes, parallel to the catalyst surface, appear by a mechanism of step flow, where the atomic layers of catalyst are "replaced" by graphene layers. More interestingly, as the catalyst particles have curved or poly-faceted surfaces, those catalyst atomic layers correspond to no definite atomic plane. The step height may thus vary along a given step flow process. Step bunching due to impeded step migration, in certain growth conditions, yields characteristic catalyst nail-head shapes. Mastering this mechanism opens up the way to tailor the structure of MWCNTs, e.g. with highly parallel carbon walls.
• Growth of individual carbon nanotubes on an array of TiN/Ni nanodots patterned by e-beam lithography and defined by dry etching for field emission application
  
  • Han Xiang-Lei
  • Mazellier Jean-Paul
  • Gangloff Laurent
  • Andrianiazy Florian
  • Chen Zhenkun
  • Cojocaru Costel Sorin
  • Maurice Jean-Luc
  • Peytavit Emilien
  • Lampin Jean-Francois
  • Legagneux Pierre
  , 2013. In this paper, we demonstrate a new technique to realize TiN/Ni nanodots array on silicon substrate using e-beam lithography and dry etching techniques. After patterning the Ni nanodisk (7 nm thick, 150 nm in diameter) at perfectly controlled location, individual vertically aligned carbon nanotubes (VACNTs) were grown using plasma-enhanced chemical-vapor deposition (PECVD). In addition, a field emission cathode (1 mm diameter circular emission area) based on a hexagonal array (20μm spacing) of individual VACNTs delivered a high emission current of 4.23 mA for an applied electric field of 22.5V/μm.
• Theoretical short-circuit current density for different geometries and organizations of silicon nanowires in solar cells
  
  • Foldyna Martin
  • Yu Linwei
  • Roca I Cabarrocas Pere
  Solar Energy Materials and Solar Cells, Elsevier, 2013, 117, pp.645–651. (10.1016/j.solmat.2012.10.014)
  DOI : 10.1016/j.solmat.2012.10.014
• Discovery of novel potent ΔF508-CFTR correctors that target the nucleotide binding domain
  
  • Odolczyk Norbert
  • Fritsch Janine
  • Norez Caroline
  • Servel Nathalie
  • da Cunha Melanie Faria
  • Bitam Sara
  • Kupniewska Anna
  • Wiszniewski Ludovic
  • Colas Julien
  • Tarnowski Krzysztof
  • Tondelier Danielle
  • Roldan Ariel
  • Saussereau Emilie L.
  • Melin-Heschel Patricia
  • Wieczorek Grzegorz
  • Lukacs Gergely L.
  • Dadlez Michal
  • Faure Grazyna
  • Herrmann Harald
  • Ollero Mario
  • Becq Frédéric
  • Zielenkiewicz Piotr
  • Edelman Aleksander
  EMBO Molecular Medicine, Wiley Open Access, 2013, 5 (10), pp.1484 - 1501. The deletion of Phe508 (ΔF508) in the first nucleotide binding domain (NBD1) of CFTR is the most common mutation associated with cystic fibrosis. The ΔF508-CFTR mutant is recognized as improperly folded and targeted for proteasomal degradation. Based on molecular dynamics simulation results, we hypothesized that interaction between ΔF508-NBD1 and housekeeping proteins prevents ΔF508-CFTR delivery to the plasma membrane. Based on this assumption we applied structure-based virtual screening to identify new low-molecular-weight compounds that should bind to ΔF508-NBD1 and act as protein-protein interaction inhibitors. Using different functional assays for CFTR activity, we demonstrated that in silico-selected compounds induced functional expression of ΔF508-CFTR in transfected HeLa cells, human bronchial CF cells in primary culture, and in the nasal epithelium of homozygous ΔF508-CFTR mice. The proposed compounds disrupt keratin8-ΔF508-CFTR interaction in ΔF508-CFTR HeLa cells. Structural analysis of ΔF508-NBD1 in the presence of these compounds suggests their binding to NBD1. We conclude that our strategy leads to the discovery of new compounds that are among the most potent correctors of ΔF508-CFTR trafficking defect known to date. (10.1002/emmm.201302699)
  DOI : 10.1002/emmm.201302699
• Experimentally obtained values of electric field of an atmospheric pressure plasma jet impinging on a dielectric surface
  
  • Sobota Ana
  • Guaitella Olivier
  • Garcia-Caurel Enric
  Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.372001. We report on experimentally obtained values of the electric field magnitude on a dielectric surface induced by an impinging atmospheric pressure plasma jet. The plasma plume was striking the dielectric surface at an angle of 45◦, at 5mm from the surface measured at the axis of the jet. The results were obtained using Pockels technique on a BSO (Bi12SiO20) crystal. A coaxial configuration of the plasma jet was used, operating in a stable mode with one bullet per voltage period, at 30 kHz and amplitude of 2 kV. The electric field was shown to be a function of the gas flow (He, at 300, 500 and 700 SCCM) and the manner in which the discharge spreads over the dielectric surface. The maximum value of 11.6 × 105Vm−1 was obtained at the negative half-period of the discharge current measured at the grounded electrode, at the flow of 300 SCCM. The largest electric field averaged over the area of the spreading of the discharge (3.6 × 105Vm−1) was found in the same conditions. (10.1088/0022-3727/46/37/372001)
  DOI : 10.1088/0022-3727/46/37/372001
• Maximum likelihood method for calibration of Mueller polarimeters in reflection configuration
  
  • Hu Haofeng
  • Garcia-Caurel Enric
  • Anna Guillaume
  • Goudail François
  Applied optics, Optical Society of America, 2013, 52, pp.6350. We address calibration of Mueller polarimeters in the presence of noise. We compare an extension of the eigenvalue calibration method (ECM) and a maximum likelihood (ML) method. The performances of these two calibration methods are investigated with numerical simulations and real experiments on a broadband infrared polarimeter. It is found that the ML method is superior to the extended ECM in terms of calibration precision and can be used at lower signal-to-noise ratio. (10.1364/AO.52.006350)
  DOI : 10.1364/AO.52.006350
• Large-Scale Simultaneous Orientation of CdSe Nanorods and Regioregular Poly(3-hexylthiophene) by Mechanical Rubbing
  
  • Hartmann Lucia
  • Djurado David
  • Florea Ileana
  • Legrand Jean-François
  • Fiore Angela
  • Reiss Peter
  • Doyle Stephen
  • Vorobiev Alexeï
  • Pouget Stéphanie
  • Chandezon Frédéric
  • Ersen Ovidiu
  • Brinkmann Martin
  Macromolecules, American Chemical Society, 2013, 46 (15), pp.6177-6186. (10.1021/ma400880x)
  DOI : 10.1021/ma400880x
• A H2-evolving photocathode based on direct sensitization of MoS3 with an organic photovoltaic cell
  
  • Bourgeteau Tiphaine
  • Tondelier Denis
  • Geffroy Bernard
  • Brisse Romain
  • Laberty-Robert Christel
  • Campidelli Stéphane
  • de Bettignies Rémi
  • Artero Vincent
  • Palacin Serge
  • Jousselme Bruno
  Energy & Environmental Science, Royal Society of Chemistry, 2013, 6, pp.2706-2713. An organic solar cell based on a poly-3-hexylthiophene (P3HT):phenyl-C61-butyric acid (PCBM) bulk hetero-junction was directly coupled to molybdenum sulfide resulting in the design of a new type of photocathode for the production of hydrogen. Both the light-harvesting system and the catalyst were deposited by low-cost solution-processed methods, i.e. spin coating and spray coating respectively. Spray-coated MoS3 films are catalytically active in strongly acidic aqueous solutions with the best efficiencies for thicknesses of 40 to 90 nm. The photocathodes display photocurrents higher than reference samples, without a catalyst or without coupling with a solar cell. Gas chromatography analysis confirms the light-induced hydrogen evolution. The addition of titanium dioxide in the MoS3 film enhances electron transport and collection within thick films and therefore the performance of the photocathode (10.1039/c3ee41321g)
  DOI : 10.1039/c3ee41321g
• PHYSICS-BASED COMPACT MODELING OF ORGANIC ELECTRONIC DEVICES
  
  • Kim Chang Hyun
  , 2013. Despite impressive progresses in organic electronic devices, a full theoretical understanding of the device operation is still lacking. The thesis is dedicated to establishing applicable theoretical descriptions of organic electronic devices, and in particular physics-based compact models. Prototypical organic diodes and transistors with various architectures are investigated, with a consistent effort to view and present the effect of charge carrier transport and injection on the observable device phenomena. A particular effort is given to integrate these models in circuit simulators, thus connecting the device-level and system-level outlooks. The approaches used comprise equivalent circuit modeling by impedance spectroscopy, analytical development of physics equations, numerical finite-element-based 2-D simulations, and experimental validations. The results provide significant understanding on the effect of traps and injection barriers on the current-voltage characteristics. Original, fully analytical compact models for rectification diodes and organic field-effect transistors are proposed with reliable numerical and experimental proofs.
• Carbon-Based Nanomaterials as an Anode for Lithium Ion Battery
  
  • Yao Fei
  • Cojocaru Costel Sorin
  , 2013. In this thesis work, carbon-based nanomaterials using as an anode for lithium ion battery have been generally investigated. Compared to typical micron-sized carbon materials, nanosized carbon materials exhibited great potentials not only in practical anode application but also in the fundamental science exploration of Li ion diffusion. In the case of practical application, one dimensional carbon nanofibers (CNFs) fabricated by electrospinning was prepared for anode material. The structure involves neither a metal substrate nor binders and therefore eventually benefited the capacity and long term stability. Yet, the energy density is still limited to 370 mAh/g of conventional carbon. In order to improve the capacity of raw carbon nanofibers, silicon, a high Li storage material, was incorporated by electrochemical deposition. The resulted Si/CNF mat improved clearly the capacity of carbon materials more than twice for most of cases. In the case of fundamental study, chemical vapor deposition (CVD)-synthesized two dimensional graphene was chosen to be a media to reveal the diffusion pathways of Li ion. Compared to typical graphite which contains both basal and edge planes, a well defined basal plane with large area can be realized in graphene to provide a comprehensive picture of lithium diffusion mechanism. We have discovered that electrochemical reaction of electrode (substrate/graphene) not only is related to the number of graphene layers but also relies on the defect sites on the basal plane of graphene. Combing the experimental results and density functional theory calculations, we proved that basal plane hindered lithium ion diffusion with a high diffusion barrier height, whereas divacancies and higher order defects can be shortcuts for lithium ion diffusion.
• Laser-induced periodic annular surface structures on fused silica surface
  
  • Liu Yi
  • Brelet Yohann
  • He Zhanbing
  • Yu Linwei
  • Forestier Benjamin
  • Deng Yongkai
  • Jiang Hongbing
  • Houard Aurélien
  Applied Physics Letters, American Institute of Physics, 2013, 102 (25), pp.251103. We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse. (10.1063/1.4812354)
  DOI : 10.1063/1.4812354
• The origins of polarimetric image contrast between healthy and cancerous human colon tissue
  
  • Novikova Tatiana
  • Pierangelo Angelo
  • Manhas Sandeep
  • Benali Abdelali
  • Validire Pierre
  • Gayet Brice
  • de Martino Antonello
  Applied Physics Letters, American Institute of Physics, 2013, 102, pp.241103. Experimentally measured spectral Mueller matrix images of ex vivo human colon tissue revealed the contrast enhancement between healthy and cancerous zones of colon specimen compared to unpolarized intensity images. Cancer development starts with abnormal changes which being not yet visible macroscopically may alter the polarization of reflected light. We have shown with experiments and modeling that light scattering by small (sub wavelength) scatterers and light absorption (mainly due to blood hemoglobin) are the key factors for observed polarimetric image contrast. These findings can pave the way for the alternative optical technique for the monitoring and early detection of cancer. (10.1063/1.4811414)
  DOI : 10.1063/1.4811414
• Rod-coil and all-conjugated block copolymers for photovoltaic applications
  
  • Yassar Abderrahim
  • Miozzo Luciano
  • Gironda Ramona
  • Horowitz Gilles
  Progress in Polymer Science, Elsevier, 2013, 38 (5), pp.791-844. Control, understanding and manipulation of the morphology and nanostructure of the active layer of bulk heterojunction solar cells are crucial for the development of polymeric solar cells. Rod-coil and all-conjugated block copolymers can self-assemble into well-ordered morphologies and provide an exciting approach to rationally design and control the nanoscale organization of these materials in organic photovoltaic devices. This article reviews the highlights of the synthesis, morphology, and properties of block copolymers for application in organic photovoltaics. Combination of the precise living polycondensation and controlled polymerization through the grafting-from or grafting-onto approaches produce various architectures of rod-coil and all conjugated block copolymers. The relationships between copolymer morphologies, physical properties and device performance are analyzed. (10.1016/j.progpolymsci.2012.10.001)
  DOI : 10.1016/j.progpolymsci.2012.10.001
• Templating and Charge Injection from Copper Electrodes into Solution-Processed Organic Field-Effect Transistors
  
  • Kim Chang Hyun
  • Hlaing Htay
  • Carta Fabio
  • Bonnassieux Yvan
  • Horowitz Gilles
  • Kymissis Ioannis
  ACS Applied Materials & Interfaces, Washington, D.C. : American Chemical Society, 2013, 5 (9), pp.3716-3721. Solution-processed organic field-effect transistors (OFETs) using chemically modified copper electrodes are reported. The purpose of this study is to shed light on the use of inexpensive copper electrodes in bottom-contact OFETs, which is consistent with the major goal of organic electronics: the realization of low-cost electronics. 6,13-Bis(triisopropylsilylethynyl)pentacene was used for solution-processed hole-transporting molecular films and pentafluorobenzenethiol was used to form self-assembled monolayers (SAMs) on the contact metals. We conducted a comparative study on copper and gold contacts and realized that, under the same performance improvement schemes, via SAM treatment and controlled crystal growth, the copper electrode device experienced a more significant enhancement than the gold electrode device. We attribute the beneficial effects of SAMs to the improved charge injection and transport properties, which are critical double effects from the fluorinated aromatic SAM structure. Grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements showed that templating property of SAMs promotes the crystallization of TIPS-pentacene films at the metal/organic interface. The presented result indicates that copper can be regarded as a promising candidate for reducing the use of gold in organic-based circuits and systems, where the cost-effective production is an important issue. (10.1021/am400325k)
  DOI : 10.1021/am400325k
• The Sense-City equipment project : insight into the prototyping and validation of environmental micro-and nanosensors for a sustainable urbanization
  
  • Lebental Bérengère
  • Angelescu Dan
  • Bourouina Tarik
  • Bourquin Frédéric
  • Cojocaru Costel-Sorin
  • Derkx François
  • Dumoulin Jean
  • Ha Thi-Lan
  • Robine Enric
  • van Damme Henri
  , 2013. While today's galloping urbanization weighs heavily on both People and Environment, the massive instrumentation of urban spaces appears a landmark toward sustainability. Collecting massively distributed information requires the use of high-performance communication systems as well as sensors with very small ecological footprint. Because of their high sensitivity, the wide range of their observables, their energetic self-sufficiency and their low cost, micro- and nano- sensors are particularly well suited to urban metrology. A 8 years, 9 MC equipment project funded by the French 'Programme d'Investissement d'Avenir' starting in 2012, the Sense-City project will offer a suite of high-quality facilities for the design, prototyping and performance assessment of micro- and nanosensors devoted to sustainable urbanization. The scientific program of Sense-City is built around four programs, environmental monitoring, structural health monitoring, energy performances monitoring and people health and exposure monitoring. We present the activities of the consortium partners, IFSTTAR, ESIEE-Paris, CSTB, LPICM, and the prospects brought by Sense-City equipment in terms of sensor prototyping, benchmarking and operation validation. We discuss how the various sensors developed by LPICM and ESIEE (for instance conformable chemical and gas microsensors using nanomaterials at LPICM, miniaturized gas chromatographs or microfluidic lab-on-chip for particles analysis at ESIEE-Paris) can be integrated by IFSTTAR into sensors networks tested by IFSTTAR and CSTB in both lab and urban settings. The massively distributed data are interpreted using advanced physical models and inverse methods in order to monitor water, air or soil quality, infrastructure and network safety, building energy performances as well as people health and exposure. We discuss the shortcomings of evaluating the performances of sensors only in lab conditions or directly in real, urban conditions. As a solution, Sense-City will provide an environment of intermediate complexity for the testing of environmental sensors, a realistic urban test space in climatic conditions, both far more complex than clean rooms and far more controllable than actual cities.
• Synthesis, characterization, morphological behaviour, and photo-and electroluminescence of highly blue-emitting fluorene-carbazole copolymers with alkyl side-chains of different lengths
  
  • Sergent Alessandra
  • Zucchi Gael
  • Pansu Robert Bernard
  • Chaigneau Marc
  • Geffroy Bernard
  • Tondelier Denis
  • Ephritikhine M.
  Journal of Materials Chemistry C, Royal Society of Chemistry, 2013, 1 (19), pp.3207-3216. Four novel phenyl-end-capped π-conjugated polymers comprising alkyl chains of different lengths were synthesized: the poly(9,9-dihexyl-2,7-fluorene-alt-9,9-dioctylfluorene) (P0), the alternating fluorene-carbazole copolymers P1 and P2 comprising 20% and 50% of carbazole, respectively, and the homopolymer poly(9-hexyl-9H-carbazole) (P3). The non-end-capped alternating fluorene-carbazole copolymer P4 comprising 20% of carbazole was also synthesized for the sake of comparison with P1. P0-P2 and P4 were synthesized by a Pd-catalyzed Suzuki-Miyaura coupling in good yields (80-89%), while P3 was obtained by a Ni-catalyzed Yamamoto coupling reaction from the 3,6-dibromocarbazole monomer in a moderate yield (52%). P0-P4 polymers were characterized by NMR, elemental analysis, and GPC. The molecular weights are 40.30, 23.42, 14.33, 3.92, and 37.49 kDa, with polydispersity indices of 2.5, 1.7, 1.8, 1.3, and 2.6, for P0, P1, P2, P3, and P4, respectively. These polymers were found to show a high thermal stability, with decomposition temperatures in the range of 395-420 °C, and the glass transition temperature was found to regularly increase with the amount of carbazole inserted in the conjugated backbone. AFM images obtained on thin films (thickness of about 90 nm) of P0-P2 revealed films with surfaces of good quality, being homogeneous with low roughness (0.2 nm for the smaller ones). These polymers were found to be blue-emitting both in diluted dichloromethane and chlorobenzene solutions as well as in thin films and exhibit relatively high values of the absolute quantum yields in the range of 100-5.5% in dichloromethane and 51.4-7.7% in thin films. Blue-emitting electroluminescent devices were obtained with P0 and P1 as emitting layers, respectively. The device built with P1 showed improved performances (EQE of 1.32%) with respect to the one built with the parent polyfluorene material (EQE of 0.75%). (10.1039/C3TC00060E)
  DOI : 10.1039/C3TC00060E
• A Compact Model for Organic Field-Effect Transistors With Improved Output Asymptotic Behaviors
  
  • Kim Chang Hyun
  • Castro-Carranza Alejandra
  • Estrada Magali
  • Cerdeira Antonio
  • Bonnassieux Yvan
  • Horowitz Gilles
  • Iñiguez Benjamin
  IEEE Transactions on Electron Devices, Institute of Electrical and Electronics Engineers, 2013, 60 (3), pp.1136-1141. Here, we propose an advanced compact analytical current-voltage model for organic field-effect transistors (OFETs), which can be incorporated into SPICE-type circuit simulators. We improved the output saturation behavior by introducing a new asymptotic function that also enables more precise low-voltage current and conductance fitting. A new expression for the subthreshold current was suggested to cover all operation regimes of OFETs. All model parameters were extracted by a systematic method, and the comparison of the modeled current with the experimental data on pentacene-based OFETs confirmed the validity of the model over a wide operation range. (10.1109/ted.2013.2238676)
  DOI : 10.1109/ted.2013.2238676
• Ciliary White Light: Optical Aspect of Ultrashort Laser Ablation on Transparent Dielectrics
  
  • Liu Yi
  • Brelet Yohann
  • He Zhanbing
  • Yu Linwei
  • Mitryukovskiy Sergey
  • Houard Aurélien
  • Forestier Benjamin
  • Couairon Arnaud
  • Mysyrowicz André
  Physical Review Letters, American Physical Society, 2013, 110 (9), pp.097601. We report on a novel nonlinear optical phenomenon, coined as ciliary white light, during laser ablation of transparent dielectrics. It is observed in 14 different transparent materials including glasses, crystals, and polymers. This phenomenon is also universal with respect to laser polarization, pulse duration, and focusing geometry. We interpret its formation in terms of the nonlinear diffraction of the laser generated white light by the ablation crater covered by nanostructures. It carries rich information on the damage profile and morphology dynamics of the ablated surface, providing a real time in situ observation of the laser ablation process. (10.1103/PhysRevLett.110.097601)
  DOI : 10.1103/PhysRevLett.110.097601