Publications

2012

• Retardation assisted enhanced Raman scattering from silicon nanostripes in the visible range
  
  • Ndong Gérald
  • Picardi Gennaro
  • Chaigneau Marc
  • Ossikovski Razvigor
  Nanotechnology, Institute of Physics, 2012, pp.035705. Patterned silicon on insulator structures representing evenly spaced parallel 15 nm-thick nanostripes exhibit an enhanced Raman scattering response when excited in the visible range in an oblique incidence backscattering configuration. The enhancement phenomenon in two structures having different stripe widths, 200 and 50 nm, is investigated at various sample azimuthal orientations, excitation radiation polarizations as well as laser wavelengths and is shown to be of resonant nature. The enhanced Raman response of the patterned structures is attributed to the presence of Mie resonances, essentially resulting in the enhancement of the internal electric field within the nanostripes. It is quantitatively described in terms of the spheroid particle model extended beyond the electrostatic limit to include field retardation effects that are shown to be responsible for the resonant behaviour in the visible range. (10.1088/0957-4484/24/3/035705)
  DOI : 10.1088/0957-4484/24/3/035705
• Investigation of deposition conditions and annealing treatments on sputtered ZnO:Al thin films: Material properties and application to microcristalline silicon solar cells
  
  • Charpentier Coralie
  , 2012. The Transparent Conductive Oxide (TCO) thin film used as a front electrode in microcrystalline silicon solar cells is a key material for the improvement of their efficiency. A promising TCO is aluminium doped zinc oxide (ZnO:Al) deposited by RF magnetron sputtering. A first part of the thesis is dedicated to the study of the influence of deposition conditions on microstructure, growth mechanisms, and opto-electronic properties of ZnO:Al thin films. We obtained an optimum in terms of maximal transparency in the visible range, and minimal resistivity, for films realized at a pressure of 0.12 Pa and at a temperature of 325 °C. A second part of the work is focused on the study of post-deposition annealing treatments, such as thermal or laser annealing processes, on the properties of the material deposited at room temperature. The influence of the annealing atmosphere (under vacuum, in N2/H2, or in pure N2) and temperature (from 400 to 500 °C) was studied. The thermal annealing step resulted in an improvement of the optical and electrical properties of the ZnO:Al thin film up to a resistivity of 3.5×10-4 Ohm.cm for a transmittance between 400 and 1000 nm of 81.2%. The laser annealing treatment influences particularly the morphological properties. The finale step of this thesis work is based on the study of the wet chemical etching of the TCO thin film, in order to create an optimal surface morphology for light confinement in the microcrystalline silicon layers without a degradation of the electrical properties. The integration of these ZnO:Al thin films as front electrodes in PIN silicon thin film solar cells was realized and investigated in depth.
• Organized growth of semiconducting one-dimensional nanostructures in vertical porous templates for the fabrication of field effect transistors
  
  • Lefeuvre Emmanuel
  , 2012. The work of this thesis has to be incorporated within the framework of the reduction of the building blocks used for the fabrication of the components in integrated circuits, and more specifically within the framework of the bottom-up approach. The main idea of this work is to use one-dimensional (1D) nanostructures as building blocks to fabricate field effect transistors. An original approach has been developed to collectively grow, handle and organize these nanostructures: the confined growth in the vertical and parallel pores provided by the self-arranged porous alumina structure. Porous anodic alumina (PAA) has been successfully synthesized on silicon substrates, and a novel porous stack has been fabricated using successive reactive ion etchings through a PAA layer as a hard mask. This porous stack is supposed to receive, organize the nanostructures, but also to provide the surrounding electrical contacts around every single nanostructure. In parallel, the growth of the 1D nanostructures that are silicon nanowires (SiNWs) and carbon nanotubes (CNTs) in PAA has been studied and optimized, using hot wire-assisted chemical vapor deposition (HWCVD). First electrical measurements, performed on SiNWs grown inside such a structure, brought evidence that a conductive path has been created by SiNWs. By investigating the electrodeposition of metallic nanoparticles inside nano-porous materials, copper, nickel and gold nanoparticles have been deposited at the bottom of vertical alumina pores, as well as inside a porous multi-layer, so as to catalyze nanostructure growth. This allowed to successfully grow both SiNWs and CNTs inside a porous multi-layer. Finally, a study based on a lithographically patterned silica mask has been carried out in order to fabricate a localized porous stack, which is essential to protect some fragile surface areas from all the transistor fabrication steps.
• La croissance plasma de nanofils de silicium catalysée par l'étain et l'indium et applications dans les cellules solaires à jonctions radiales.
  
  • O'Donnell Benedict
  , 2012. Cette thèse présente des cellules solaires en silicium deposées par plasma dans lesquelles la lumière est piégée par un réseau désorganisé de nanofils de silicium. Le dépôt sous vide des nanofils permet de contourner les étapes de texturation de substrat typiquement requises pour augmenter le parcours moyen des photons dans les cellules solaires en couches minces classiques. Des gouttes d'étain et d'indium servant à catalyser la croissance de ces nanofils ont été déposées et disposées sous vide sur des substrats d'oxide trasparent conducteur. Des agencements de gouttes métalliques aux diamètres et densités couvrant plusieurs ordres de grandeur ont été obtenus en optimisant les matériaux et les conditions de dépôt utilisés. En comparant l'aptitude de différents métaux à catalyser la croissance de nanofils de silicium, des distinctions majeures ont été établies entre les métaux de transition et Sn, In, Bi, Ga, Pb et Al. Le cas des nanofils de silicium catalysés par des gouttes d'étain a été étudié en profondeur. Des réseaux désorganisés de nanofils dopés de type P ont été recouverts de couches de silicium amorphe hydrogéné intrinsèque et dopés N, ainsi que d'une couche d'oxide d'ITO pour former des réseaux de 107 jonctions PIN radiales couvrant des surfaces de 3,1 mm². Ces cellules présentent des tensions à circuit ouvert de 0,8 V et des courants de court-circuit de 13 mA/cm² bien qu'elles soient entièrement déposées par des étapes sous vide sur des substrats non texturés.
• Different mechanisms of graphene wall nucleation on Fe and Ni particles
  
  • Maurice Jean-Luc
  • He Zhanbing
  • Cojocaru Costel Sorin
  Advances in Imaging and Electron Physics, Elsevier, 2013, 179, pp.142. We compare, by in situ annealing of carbon nanofibres (CNFs) in the TEM, the catalytic activities of Ni and Fe for the nucleation of graphene layers. Graphene planes that are at an angle with the metal are dissolved in the case of Ni, while new graphene layers are generated parallel to the surface. In the case of Fe, we see no evolution of the particle in the same conditions, unless we start from an amorphized CNF. In that case, the amorphous carbon is easily dissolved into the Fe. These dissolved carbon atoms get out of the particle in the form of a new nanotube, where nucleation takes place - partly at least - perpendicular to the Fe surface. (10.1016/B978-0-12-407700-3.00002-8)
  DOI : 10.1016/B978-0-12-407700-3.00002-8
• Nanopatterned front contact for broadband absorption in ultra-thin amorphous silicon solar cells
  
  • Massiot I.
  • Colin Clément
  • Péré-Laperne Nicolas
  • Roca I Cabarrocas Pere
  • Sauvan Christophe
  • Lalanne Philippe
  • Pelouard Jean-Luc
  • Collin Stéphane
  Applied Physics Letters, American Institute of Physics, 2012, 101 (16), pp.163901. Broadband light trapping is numerically demonstrated in ultra-thin solar cells composed of a flat amorphous silicon absorber layer deposited on a silver mirror. A one-dimensional silver array is used to enhance light absorption in the visible spectral range with low polarization and angle dependencies. In addition, the metallic nanowires play the role of transparent electrodes. We predict a short-circuit current density of 14:6mA=cm2 for a solar cell with a 90 nm-thick amorphous silicon absorber layer. (10.1063/1.4758468)
  DOI : 10.1063/1.4758468
• Low‐Temperature & Transfer‐Free Graphene Growth: Process and Underlying Mechanisms
  
  • Lee Chang Seok
  , 2012. In this thesis work, we developed a new paradigm in the field of graphene growth, based on PECVD and Ion Implantation techniques. Exposure of the metal film to highly reactive plasma introduces carbon atoms at and near the film surface; performing this at elevated temperature makes the carbon atoms to diffuse throughout the film.After adapting this method to graphene growth, it delivered graphene layers on Ni at 450 °C. Moreover, in addition to the top‐surface layer, we obtained with this technique another graphene layer inbetween Ni and the underlying insulating substrate (SiO2 or glass). That second graphene layer placing itself directly on the insulating (functional) substrate, we developed a simple process for using it directly as a sensor without transfer. We were the first to propose carbon ion implantation for supplying carbon atoms to the Ni layer, prior to obtaining graphene upon annealing. By separating introduction and annealing, this technique allowed us to isolate important factors of a heat treatment. We were thus able, by using this method, to get fundamental insight into the graphene growth mechanisms. Due to fast diffusion, the final carbon distribution in a Ni film depends on the details of the annealing treatment that is applied during or after carbon has been introduced. We show in particular that two kinds of graphitic materials are obtained after a given treatment: one under the form of single crystals of few‐layer graphene/graphite, grown during the high temperature plateau, and a second under the form of nanocrystalline few‐layer graphene, grown during cooling.Finally, on the graphene grown by PECVD directly on glass at low temperature, we thus developed a humidity sensor, by direct electrode printing. Beyond this proof of concept, we need to further investigate growth mechanisms and annealing conditions for the development of various transfer‐free, low‐temperature, graphene applications.
• Hydrogenated polymorphous silicon: establishing the link between hydrogen microstructure and irreversible solar cell kinetics during light soaking
  
  • Kim Ka-Hyun
  , 2012. This thesis is dedicated to hydrogenated polymorphous silicon (pm-Si:H) and solar cells based on this material. pm-Si:H is a nanostructured thin film deposited by conventional PECVD method. The effects of various deposition parameters (gas flow ratio, pressure, RF power, Ts) on material properties were investigated in order to optimize its quality. The strategy was to combine a wide range of diagnostics (spectroscopic ellipsometry, hydrogen exodiffusion, SIMS, FTIR, AFM, etc.). Due to the contribution of plasma synthesized silicon nanoparticles, the process condition of pm-Si:H shows the difference in contrary to a-Si:H deposition through ionized radicals. Studies on pm-Si:H deposition process allows to fabricate pm-Si:H PIN solar cells with a high initial efficiency of 9.22 % and fill factor of 74.1, but also demonstrate unusual light-induced effects, namely i) a rapid initial degradation, ii) an irreversible degradation, and iii) large macroscopic structural changes. Comprehensive investigation on the light-induced degradation kinetics of pm-Si:H PIN layer stacks reveals a pronounced hydrogen accumulation and delamination at the substrate/p-type layer interface under light-soaking, leading to macroscopic structural changes, e.g., peel-off and solar cell area loss. We have found that a PIN structure leads to facilitated delamination during lightsoaking, which we attribute to hydrogen accumulation at the substrate/p-layer interface, while use of a NIP structure prevents the hydrogen accumulation and delamination. This lead us to fabricate pm-Si:H NIP solar cells showing a high stabilized efficiency of 8.43 %, that shows a small (10 %) light-induced degradation after light-soaking for 500 hours.
• Effects of acid-treated silicon nanowires on hybrid solar cells performance
  
  • Jeon Taewoo
  • Geffroy Bernard
  • Tondelier Denis
  • Yu Linwei
  • Jegou Pascale
  • Jousselme Bruno
  • Palacin Serge
  • Roca I Cabarrocas Pere
  • Bonnassieux Yvan
  Solar Energy Materials and Solar Cells, Elsevier, 2012, pp.http://dx.doi.org/10.1016/j.solmat.2012.09.015. We demonstrate the efficiency improvement of hybrid solar cells based on silicon nanowires (SiNWs) and organic materials. This progress is readily achieved by acid treatments of SiNWs. Tin (Sn) catalyzed SiNWs contain residual Sn and Sn oxide drops on their top which are deleterious for a solar cell performance. Removal of this Sn and Sn oxide contamination is performed with hydrochloric acid. X-ray photoelectron spectroscopy measurement verified that the amount of Sn and Sn oxide on SiNWs array is decreased according to the immersing time. This brings open-circuit voltage and shunt resistance increase thus the hybrid solar cell performance is improved. Light intensity dependent open-circuit voltage clearly reveals that this efficiency improvement results from a reduced trap-assisted recombination through Sn and Sn oxide. In addition to the residual catalysts removal, native oxide removal by hydrofluoric acid also considerably contributes to further improvement in terms of short-circuit current and fill factor. Clearly, the improvement of SiNWs quality is essential for an optimization of hybrid solar cell performance. (10.1016/j.solmat.2012.09.015)
  DOI : 10.1016/j.solmat.2012.09.015
• Low Temperature Plasma Synthesis of Nanocrystals and their Application to the Growth of Crystalline Silicon and Germanium Thin Films
  
  • Roca I Cabarrocas Pere
  • Kim Ka-Hyun
  • Cariou Romain
  • Labrune Martin
  • Johnson Erik
  • Moreno M.
  • Torres Rio A.
  • Abolmasov Sergey
  • Kasouit Samir
  MRS Online Proceedings Library, Cambridge University Press, 2012, 1426, pp.319. We summarize our research studies on the synthesis of silicon and germanium nanocrystals and their application to the growth of a variety of thin films, spanning the range from fully disordered amorphous up to fully ordered crystalline. All these films are deposited in a standard radio-frequency glow discharge system at low temperature (~200 °C). We show how the plasma synthesis of silicon nanocrystals, initially a side effect of powder formation, has become over the years an exciting field of research which has opened the way to new opportunities in the field of materials deposition and their application to optoelectronic devices. Our results suggest that epitaxy requires the melting/amorphization of the nanocrystals upon impact on the substrate, the subsequent epitaxial growth being favored on (100) c-Si substrates. As a consequence, the control of the impact energy is a critical aspect of the growth which will require new strategies such as the use of tailored voltage waveforms. (10.1557/opl.2012.1094)
  DOI : 10.1557/opl.2012.1094
• Synthèse du graphène par implantation ionique dans des substrats métalliques
  
  • Le Normand F.
  • Lee C.S.
  • Maurice J.L.
  • Cojocaru C.S.
  • Châtelet Marc
  • Chaigneau M.
  • Muller D.
  • Speisser C.
  • Gutierrez G.
  , 2012.
• Ion beam synthesis of graphene by carbon implantation into metallic precursors
  
  • Lee C.S.
  • Gutierrez G.
  • Muller D.
  • Speisser C.
  • Cojocaru C.S.
  • Châtelet Marc
  • Chaigneau M.
  • Le Normand F.
  , 2012.
• Effect of the anodization voltage on the porewidening rate of nanoporous anodic alumina
  
  • Mahbubur Rahman Mohammad
  • Garcia-Caurel Enric
  • Santos Abel
  • Marsal Lluis F.
  • Pallares Josep
  • Ferre-Borrull Josep
  Nanoscale Research Letters, SpringerOpen, 2012, 7, pp.474. A detailed study of the pore-widening rate of nanoporous anodic alumina layers as a function of the anodization voltage was carried out. The study focuses on samples produced under the same electrolyte and concentration but different anodization voltages within the self-ordering regime. By means of ellipsometry-based optical characterization, it is shown that in the porewidening process, the porosity increases at a faster rate for lower anodization voltages. This opens the possibility of obtaining three-dimensional nanostructured nanoporous anodic alumina with controlled thickness and refractive index of each layer, and with a refractive index difference of up to 0.24 between layers, for samples produced with oxalic acid electrolytes. (10.1186/1556-276X-7-474)
  DOI : 10.1186/1556-276X-7-474
• Silicon epitaxy below 200°C: Towards thin crystalline solar cells
  
  • Cariou Romain
  • Ruggeri R.
  • Chatterjee P.
  • Gentner J.L.
  • Roca I Cabarrocas Pere
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2012, 8470, pp.84700B. Low temperature plasma processes provide a toolbox for etching, texturing and deposition of a wide range of materials. Here we present a bottom up approach to grow epitaxial crystalline silicon films (epi-Si) by standard RF-PECVD at temperatures below 200°C. Booth structural and electronic properties of the epitaxial layers are investigated. Proof of high crystalline quality is deduced from spectroscopic ellipsometry and HRTEM measurements. Moreover, we build heterojunction solar cells with intrinsic epitaxial absorber thickness in the range of a few microns, grown at 175 °C on highly doped (100) substrates, in the wafer equivalent approach. Achievement of a fill factor as high as 80 % is a proof that excellent quality of epitaxial layers can be produced at such low temperatures. While 8.5 % conversion efficiency has already been achieved for a 3.4 µm epitaxial silicon absorber, the possibility of reaching 15 % conversion efficiency with few microns epi-Si is discussed based on a detailed opto-electrical modeling of current devices. (10.1117/12.929741)
  DOI : 10.1117/12.929741
• Bismuth-Catalyzed and Doped Silicon Nanowires for One-Pump-Down Fabrication of Radial Junction Solar Cells
  
  • Yu Linwei
  • Fortuna Franck
  • O'Donnell Benedict
  • Jeon Taewoo
  • Foldyna Martin
  • Picardi Gennaro
  • Roca I Cabarrocas Pere
  Nano Letters, American Chemical Society, 2012, 12, pp.4153-4158. Silicon nanowires (SiNWs) are becoming a popular choice to develop a new generation of radial junction solar cells. We here explore a bismuth- (Bi-) catalyzed growth and doping of SiNWs, via vapor-liquid-solid (VLS) mode, to fabricate amorphous Si radial n-i-p junction solar cells in a one-pump-down and low-temperature process in a single chamber plasma deposition system. We provide the first evidence that catalyst doping in the SiNW cores, caused by incorporating Bi catalyst atoms as n-type dopant, can be utilized to fabricate radial junction solar cells, with a record open circuit voltage of V-oc = 0.76 V and an enhanced light trapping effect that boosts the short circuit current to J(sc) = 11.23 mA/cm(2). More importantly, this bi-catalyzed SiNW growth and doping strategy exempts the use of extremely toxic phosphine gas, leading to significant procedure simplification and cost reduction for building radial junction thin film solar cells. (10.1021/NL3017187)
  DOI : 10.1021/NL3017187
• Transparent and air stable organic field effect transistors with ordered layers of dibenzo[d,d]thieno[3,2-b;4,5-b′]dithiophene obtained from solution
  
  • Marszalek T.
  • Kucinska M.
  • Tszydel I.
  • Gravalidis C.
  • Kalfagiannis N.
  • Logothetidis S.
  • Yassar A.
  • Miozzo L.
  • Nosal A.
  • Gazicki-Lipmane M.
  • Jung Julien
  • Ulanski J.
  Optical Materials, Elsevier, 2012, 34 (10), pp.1660-1663. In a search for solution processable and stable p-type semiconductors an analogue of pentacene namely dibenzo[d,d]thieno[3,2-b;4,5-b′]dithiophene (DBTDT) - was tested as an active layer in organic field effect transistors (OFETs). It was found that thin, continuous and transparent films of DBTDT can be obtained with the help of solution based zone-casting technique. This deposition technique allows one to produce highly oriented crystalline layers of DBTDT showing similar molecular arrangement as that of a single crystal. The zone-cast layers of DBTDT were successfully applied in a fabrication process of OFETs with Parylene C® used as the gate dielectric. The best parameters are exhibited by the devices with the bottom-gate, top contact configuration: charge carrier mobility of ca 0.02 cm2/Vs and threshold voltage of ca −50 V and performance of these OFETs remains unchanged after 1 months storage in air. (10.1016/j.optmat.2012.03.008)
  DOI : 10.1016/j.optmat.2012.03.008
• Raman spectroscopy and polarization: Selected case studies
  
  • Ossikovski Razvigor
  • Picardi Gennaro
  • Ndong Gérald
  • Chaigneau Marc
  Comptes Rendus. Physique, Académie des sciences (Paris), 2012, 13, pp.837-852. We show, through several selected case studies, the potential benefits that can be obtained by controlling the polarization states of the exciting and scattered radiations in a Raman scattering experiment. When coupled with polarization control, Raman spectroscopy is thus capable of providing extra information on the structural properties of the materials under investigation. The experimental examples presented in this work are taken from the area of both conventional, i.e., far-field, as well as from near-field Raman spectroscopy. They cover topics such as the stress tensor measurement in strained semiconductor structures, the vibration mode assignment in pentacene thin films and the Raman scattering tensor determination from near-field measurements on azobenzene monolayers. The basic theory necessary for modelling the far- and near-field polarized Raman responses is also given and the model efficiency is illustrated on the experimental data. (10.1016/j.crhy.2012.06.001)
  DOI : 10.1016/j.crhy.2012.06.001
• Current Saturation in Field Emission from H-Passivated Si Nanowires
  
  • Choueib May
  • Martel Richard
  • Cojocaru Costel Sorin
  • Ayari Anthony
  • Vincent Pascal
  • Purcell Stephen T.
  ACS Nano, American Chemical Society, 2012, 6 (8), pp.7463-7471. This paper explores the field emission (FE) properties of highly crystalline Si nanowires (NWs) with controlled surface passivation. The NWs were batch-grown by the vapor_liquid_solid process using Au catalysts with no intentional doping. The FE current_voltage characteristics showed quasi-ideal current saturation that resembles those predicted by the basic theory for emission from semiconductors, even at room temperature. In the saturation region, the currents were extremely sensitive to temperature and also increased linearly with voltage drop along the nanowire. The latter permits the estimation of the doping concentration and the carrier lifetime, which is limited by surface recombination. The conductivity could be tuned over 2 orders of magnitude by in situ hydrogen passivation/desorption cycles. This work highlights the role of dangling bonds in surface leakage currents and demonstrates the use of hydrogen passivation for optimizing the FE characteristics of Si NWs. (10.1021/nn302744e)
  DOI : 10.1021/nn302744e
• Charge transfers from doped silicon nanocrystals probed by non-contact atomic force microscopy
  
  • Borowik Lukasz
  • Deresmes D.
  • Nguyen-Tran Thuat
  • Roca I Cabarrocas Pere
  • Melin Thierry
  , 2012.
• Influence of bistatic angle and forest structure description on classical polarimetric parameters
  
  • Everaere Etienne
  • Colin-Koeniguer Elise
  • Thirion-Lefèvre Laetitia
  • de Martino Antonello
  , 2012, pp.6531-6534. In this paper, we present numerical simulations of forest scattering in bistatic configuration. The aim is to compare the influence of the structure of the forest on typical measurement parameters in a bistatic and polarimetric framework. Bistatic configuration pledges advantages of cost and stealth. The scattering model COBISMO has been developped to simulate such configurations. Simulations are performed on four forest structures with different dispositions of branches. Results show an important influence of branch inclinations but not a real influence of their position. (10.1109/IGARSS.2012.6352754)
  DOI : 10.1109/IGARSS.2012.6352754
• Amplificateur optique hybride SOA-Raman à bande passante optimisée (89nm) pour les réseaux CWDM
  
  • Motaweh Tammam
  • Sharaiha Ammar
  • Ghişa Laura
  • Morel Pascal
  • Guegan Mikael
  • Brenot Romain
  • Lelarge François
  , 2012.
• Electrical-field-induced structural change and charge transfer of lanthanide-salophen complexes assembled on carbon nanotube field effect transistor devices.
  
  • Magadur Gurvan
  • Bouanis Fatima Zara
  • Norman Evgeny
  • Guillot Regis
  • Lauret Jean‐sébastien
  • Huc Vincent
  • Cojocaru Costel Sorin
  • Mallah Talal
  Chemical Communications, Royal Society of Chemistry, 2012, 48, pp.9071-9073. The application of a negative gate voltage on a carbon nanotube field effect transistor decorated by a binuclear Tb(III) complex leads to the generation of a negatively charged mononuclear one, presenting an electron density transfer to the nanotube and ambipolar behaviour. (10.1039/c2cc34134d)
  DOI : 10.1039/c2cc34134d
• The Sense-City project
  
  • Derkx François
  • Lebental Bérengère
  • Bourouina Tarik
  • Bourquin Frédéric
  • Cojocaru Costel-Sorin
  • Robine Enric
  • van Damme Henri
  , 2012, pp.9p. A large scale equipment project, the Sense-City Equipex has received support from the French government in the framework of the 'Programme d’Investissement d’Avenir'. This project is led by the French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR) with ESIEE-Paris, the Laboratory of Physics of Interfaces and Thin Films (LPICM) and the Scientific and Technical Centre for Building (CSTB) as consortium partners. Starting in 2012, Sense-City will offer a suite of high-quality facilities for the design, prototyping and performance assessment of innovative, micro- and nanotechnology based sensors devoted to urban instrumentation. Acknowledging the shortcomings of evaluating sensors performances in laboratory conditions only or in the ever-changing environment of our cities, Sense-City will provide a realistic urban test space in climatic conditions, far more complex than clean rooms and far less complex than actual cities. Sense-city revolves around the 'mini-city' concept, a large, fully customizable climatic hall able to host full- and reduced-scale models of essential urban components. The design of the models will allow for the simulation in climatic conditions of numerous scenarios of sustainable cities. The scenarios to be implemented will correspond to different research topics related to urban sustainability: energy performances in buildings, quality of air, water and soils, quality of fluid distribution networks (gas, sewage, drink water), control of waste disposal areas, durability and safety of infrastructures.
• Synthesis of conducting transparent few-layer graphene directly on glass at 450 °C
  
  • Lee Chang Seok
  • Sorin Cojocaru Costel
  • Moujahid Waleed
  • Lebental Bérengère
  • Chaigneau Marc
  • Châtelet Marc
  • Le Normand François
  • Maurice Jean-Luc
  Nanotechnology, Institute of Physics, 2012, 23, pp.5603. Post-growth transfer and high growth temperature are two major hurdles that research has to overcome to get graphene out of research laboratories. Here, using a plasma-enhanced chemical vapour deposition process, we demonstrate the large-area formation of continuous transparent graphene layers at temperatures as low as 450 °C. Our few-layer graphene grows at the interface between a pre-deposited 200 nm Ni catalytic film and an insulating glass substrate. After nickel etching, we are able to measure the optical transmittance of the layers without any transfer. We also measure their sheet resistance directly and after inkjet printing of electrical contacts: sheet resistance is locally as low as 500 Ω sq-1. Finally the samples equipped with printed contacts appear to be efficient humidity sensors. (10.1088/0957-4484/23/26/265603)
  DOI : 10.1088/0957-4484/23/26/265603
• Magnetic properties of structurally characterized binuclear lanthanide complexes bridged by 2,2′-bipyrimidine
  
  • Zucchi Gaël
  • Le Goff X. F
  Polyhedron, Elsevier, 2012, 52, pp.1262. A family of five homobimetallic complexes with magnetically-active trivalent lanthanides of the second half of the series with general formula [{Ln(tta)3}2(μ-bpm)] (Ln = Gd, Tb, Dy, Ho, Er, tta = 2-thenoyltrifluoroacetonato, bpm = 2,2′-bipyrimidine) has been structurally characterized by X-ray diffraction and the magnetic properties of these complexes are reported. The two lanthanide ions are coordinated to the bridging bpm ligand which connects the two metallic centers. The magnetic behavior of these complexes has been investigated. It revealed that a weak antiferromagnetic coupling is observed with the TbIII, DyIII, HoIII, and ErIII ions while a very weak ferromagnetic exchange between the two GdIII ions was observed. (10.1016/j.poly.2012.06.021)
  DOI : 10.1016/j.poly.2012.06.021