Publications

2014

• General criterion for the physical realizability of the differential Mueller matrix
  
  • Ossikovski Razvigor
  • Devlaminck Vincent
  Optics Letters, Optical Society of America - OSA Publishing, 2014, 39 (5), pp.1216-1219. In this Letter, we derive a general criterion for the physical realizability of the differential Mueller matrix m of a depolarizing continuous medium. The criterion is based on checking the positive semidefiniteness of a 3×3 restriction of the coherency matrix of the G-symmetric component of m and turns out be a close analogue of the well-known criterion of Cloude for a Mueller matrix to be physically realizable. The related aspects of local and global, as well as Stokes and physical (or Cloude), realizabilities are discussed comparatively. The practical application of the criterion, in connection with the above types of realizabilities, is illustrated on experimental Mueller matrices from the literature.
• Corrosion under argon irradiation of titanium in the low MeV range: A study coupling AFM and Spectroscopic Ellipsometry
  
  • Do Ngoc-Long
  • Garcia-Caurel Enric
  • Bérerd N.
  • Moncoffre N.
  • Gorse-Pomonti Dominique
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2014, 327, pp.47-51. This paper reports on a recent study of the corrosion under argon ion irradiation of titanium in the low MeV range (1-9 MeV), associating AFM and Spectroscopic Ellipsometry. Irradiation with MeV Arn+ (n = 1, 3) ions produces damages on the titanium surface. Large craters form on the oxidized titanium surface whose characteristics vary as a function of the argon energy between 2 and 9 MeV. The superficial oxide grows thicker under irradiation over the same energy range, especially near 3 MeV. It is suggested that collisions cascades play a significant role in the overall damage process. (10.1016/j.nimb.2013.09.049)
  DOI : 10.1016/j.nimb.2013.09.049
• Blue light absorption enhancement based on vertically channelling modes in nano-holes arrays
  
  • Gomard Guillaume
  • Peretti Romain
  • Callard Ségolène
  • Meng Xianqin
  • Artinyan Rémy
  • Deschamps Thierry
  • Cabarrocas Pere Roca I.
  • Drouard Emmanuel
  • Seassal Christian
  Applied Physics Letters, American Institute of Physics, 2014, 104 (5), pp.051119. We investigate the specific optical regime occurring at short wavelengths, in the high absorption regime, in silicon thin-films patterned by periodically arranged nano-holes. Near-field scanning optical microscopy indicates that the incoming light is coupled to vertically channelling modes. Optical modelling and simulations show that the light, travelling inside the low-index regions, is absorbed at the direct vicinity of the nano-holes sidewalls. This channelling regime should be taken into account for light management in optoelectronic devices. (10.1063/1.4864267)
  DOI : 10.1063/1.4864267
• Compact DC modeling of organic field-effect transistors: Review and perspectives
  
  • Kim Chang-Hyun
  • Bonnassieux Yvan
  • Horowitz Gilles
  IEEE Transactions on Electron Devices, Institute of Electrical and Electronics Engineers, 2014, 61 (2), pp.278-287. In spite of impressive improvements achieved for organic field-effect transistors (OFETs), there is still a lack of theoretical understanding of their behaviors. Furthermore, it is challenging to develop a universal model that would cover a huge variety of materials and device structures available for state-of-the-art OFETs. Nonetheless, currently there is a strong need for specific OFET compact models when device-to-system integration is an important issue. We briefly describe the most fundamental characters of organic semiconductors and OFETs, which set the bottom line dictating the requirement of an original model different from that of conventional inorganic devices. Along with an introduction to the principles of compact modeling for circuit simulation, a comparative analysis of the reported models is presented with an emphasis on their primary assumptions and applicability aspects. Critical points for advancing OFET compact models are discussed in consideration of the recent understanding of device physics. (10.1109/TED.2013.2281054)
  DOI : 10.1109/TED.2013.2281054
• Molecular dynamics simulations of H-induced plasma processes and cluster-catalyzed epitaxial growth of thin silicon films
  
  • Le Ha-Linh Thi
  , 2014. Three different processes taking place in a plasma reactor; namely, heating and melting of plasma-born hydrogenated silicon clusters by reactions with atomic hydrogen, hydrogen-induced healing of cluster-damaged silicon surfaces, and cluster-catalyzed epitaxial growth of thin silicon films have been investigated by means of molecular dynamics simulations. Two plasma-born hydrogenated silicon clusters representing amorphous and crystalline structures are chosen to be exposed to atomic hydrogen as in a realistic plasma reactor. We investigate quantitatively how the clusters heat up and melt by the subsequent reactions with H-atoms. A silicon surface which was partly damaged by a too violent cluster impact has been treated by hydrogen atoms. We have observed that the ill-defined silicon surface is rearranged to its initial crystalline structure after the exposure with atomic hydrogen if the appropriate H-atom flux is chosen; i.e., due to the surface reaction dynamics with hydrogen atoms, the silicon atoms of the investigated hydrogenated silicon cluster are positioned in an epitaxial surface structure. We have performed an in-depth study of the deposition dynamics of hydrogenated silicon clusters on a crystalline silicon substrate by controlling the parameters governing the cluster surface deposition. We have found that epitaxial growth of thin silicon films can be obtained from cluster deposition if the impact energies are sufficiently high for cluster atoms and surface atoms touching the cluster to undergo a phase transition to the liquid state before being recrystallized in an epitaxial order. Yet more strikingly, by applying a non-normal incidence angle for the impinging clusters, the epitaxial growth efficiency could considerably be enhanced. Those findings are crucially important to improve the high-speed growth of epitaxial silicon thin films at low temperatures using Plasma-Enhanced Chemical Vapor Deposition (PECVD) techniques for industrial applications.
• Simplified calibration procedure for Mueller polarimeter in transmission configuration
  
  • Hu Haofeng
  • Garcia-Caurel Enric
  • Anna Guillaume
  • Goudail François
  Optics Letters, Optical Society of America - OSA Publishing, 2014, 39 (3), pp.418. We address calibration of Mueller polarimeters in transmission configuration and in the presence of noise. By comparing the maximum likelihood (ML) method and the extended eigenvalue calibration method, it is found that the ML method yields higher precision in the presence of noise. Moreover, we show that by employing the ML method together with simple constraints on the calibration matrices, it is possible to perform the calibration without using a retarder, and with only polarizers. This result is of great interest for the calibration of multispectral polarimeters. (10.1364/OL.39.000418)
  DOI : 10.1364/OL.39.000418
• Determination of thicknesses of oxide films grown on titanium under argon irradiation by spectroscopic ellipsometry
  
  • Do Ngoc-Long
  • Garcia-Caurel Enric
  • Bererd Nicolas
  • Moncoffre Nathalie
  • Gorse-Pomonti Dominique
  Journal of Nuclear Materials, Elsevier, 2014, 447 (1-3), pp.197-207. In this article we present a study of the oxidation of pure titanium bulk samples under argon ion irradiation at 500°C under rarefied air. In particular we follow the dependence of the oxide thickness as a function of the energy of argon ions. The novelty of this study consists in the range of ion energy explored, from 1 to 9MeV. Until very recently it was commonly accepted that metal surfaces were transparent to ion beams in this low energy range (few MeV), and no surface modifications were expected. In a previous paper by the authors of this work, the formation of shallow craters in the surface of titanium was reported as a result of argon ion bombardment with energies of 2, 4 and 9MeV under the same environmental conditions. We show here that around 3MeV the oxide growth is unexpectedly enhanced. We think that an interplay of electronic excitations and nuclear ballistic collisions could possibly explain this enhanced oxide growth. We have used spectroscopic visible ultraviolet ellipsometry and XPS to determine the thickness of the oxide layers and characterize their optical properties. From the optical properties of the oxides we observed that for ion energies below 3-4MeV the oxides show a dielectric-like behavior, whereas for ion energies above 3-4MeV the oxides show a metal-like behavior. These findings indicate also that ion bombardment in this energy range may change substantially the oxygen-to-titanium ratio in the oxide films grown under irradiation leading to the formation of titanium sub-oxides. (10.1016/j.jnucmat.2014.01.010)
  DOI : 10.1016/j.jnucmat.2014.01.010
• Modeling the optical properties of self-organized arrays of liquid crystal defects
  
  • Coursault Delphine
  • Ibrahim Bicher Haj
  • Pelliser Laurent
  • Zappone Bruno
  • de Martino Antonello
  • Lacaze Emmanuelle
  • Gallas Bruno
  Optics Express, Optical Society of America - OSA Publishing, 2014, 22 (19), pp.23182-23191. Local full Mueller matrix measurements in the Fourier plane of a microscope lens were used to determine the internal anisotropic ordering in periodic linear arrays of smectic liquid crystal defects, known as 'oily streaks'. We propose a single microstructure-dependent model taking into account the anisotropic dielectric function of the liquid crystal that reproduces the smectic layers orientation and organization in the oily streaks. The calculated Mueller matrix elements are compared to the measured data to reveal the anchoring mechanism of the smectic oily streaks on the substrate and evidence the presence of new type of defect arrangement. Beyond the scientific inquiry, the understanding and control of the internal structure of such arrays offer technological opportunities for developing liquid-crystal based sensors and self-assembled nanostructures. (10.1364/OE.22.023182)
  DOI : 10.1364/OE.22.023182
• Substrate and p-layer effects on polymorphous silicon solar cells
  
  • Abolmasov S.N.
  • Woo H.
  • Planques R.
  • Holovský J.
  • Johnson E.V.
  • Purkrt A.
  • Roca I Cabarrocas P.
  EPJ Photovoltaics, EDP sciences, 2014, 5. (10.1051/epjpv/2014007)
  DOI : 10.1051/epjpv/2014007
• Sol-gel route toward efficient and robust Distributed Bragg Reflector for light management applications
  
  • Brudieu Barbara
  • Le Bris Arthur
  • Teisseire Jérémie
  • Guillemot François
  • Dantelle Géraldine
  • Misra S.
  • Cabarrocas Pere Roca I.
  • Sorin Fabien
  • Gacoin Thierry
  Advanced Optical Materials, Wiley, 2014. The optimization of functional optical devices requires the appropriate control of light propagation, which can be achieved by using engineered dielectric structures. Innovative materials combination and fabrication strategies are required to achieve a robust gain in performance without impacting manufacturing complexity and cost. In the present work, a novel liquid-based approach is proposed for the simple and scalable fabrication of highly effi - cient and robust optical multilayer dielectric coatings. In particular, a sol-gel process is developed that enables the fabrication of large-area distributed Bragg refl ectors (DBR) integrating macroporous materials of controlled closed porosity. The DBRs have a very high index contrast, excellent and tunable optical properties, and high stability of performance and structural integrity with respect to crack formation and delamination, even against harsh ageing tests or solvent exposure. The potential of this approach to be integrated within existing optoelectronic architectures is demonstrated through the integration of a DBR structure as a back refl ector in an amorphous silicon solar cell (a-Si:H), resulting in a signifi cant increase in light absorption, photocurrent, and overall effi ciency. This opens the way towards simple dielectric engineering of robust photoactive devices based on the versatile use of liquid routes for the deposition of structured dielectric coatings. (10.1002/adom.201400292)
  DOI : 10.1002/adom.201400292
• Exploiting the potential of 2-((5-(4-(diphenylamino)phenyl)thiophen-2-yl)methylene)malononitrile as an efficient donor molecule in vacuum-processed bulk-heterojunction organic solar cells
  
  • Choi Jin Woo
  • Kim Chang-Hyun
  • Pison Jonathan
  • Oyedele Akinola
  • Tondelier Denis
  • Leliège Atoine
  • Kirchner Eva
  • Blanchard Philippe
  • Roncali Jean
  • Geffroy Bernard
  RSC Advances, Royal Society of Chemistry, 2014, 4 (10), pp.5236-5242. A comprehensive experimental study is reported on the optical and electrical characteristics of 2-((5-(4-(diphenylamino)phenyl)thiophen-2-yl)methylene)malononitrile (DPTMM) when used as molecular donor in an organic solar cell (OSC) device structure. A major property of this new donor-type material is an unusually deep highest-occupied molecular orbital (HOMO) level that leads to a high open-circuit voltage (Voc). A reasonably high hole-mobility was also observed in a hole-injection diode configuration. These are both promising factors for high-performance OSCs. In order to fully explore the potential of DPTMM in bulk-heterojunction-based OSCs, a step-wise experimental strategy was applied to optimize film composition and cell architecture. By co-evaporating the DPTMM with C60 to promote exciton dissociation by maximizing the heterojunction area power conversion efficiency (PCE) of 3.0% was achieved. Finally, inserting a buffer layer and a spatial gradient of the donor/acceptor ratio was found to provide better conduction paths for charge carriers. The maximum obtained PCE was 4.0%, which compares favorably with the state-of-the-art of high-performance OSCs. All optimized devices show quite unusual high Voc values up to 1 V. (10.1039/C3RA47059H)
  DOI : 10.1039/C3RA47059H
• One−pot Route To Class II Hybrid Ionogels Electrolytes
  
  • Fontaine Olivier
  • Touidjine Amina
  • Maréchal Manuel
  • Bonhomme Christian
  • Ribot François
  • Geffroy Bernard
  • Jousselme Bruno
  • Sanchez Clément
  • Laberty-Robert Christel
  New Journal of Chemistry, Royal Society of Chemistry [1987-....], 2014, 38 (5), pp.2008-2015. A new system based on class II hybrid ionogels (Si-IL gels) has been developed for overcoming leaking problems associated with liquid electrolytes in dye-sensitized solar cells (DSSCs). We co-condensed a silica precursor with an alkoxysilane functionalized ionic liquid precursor, under acidic conditions, to obtain a hybrid ionogel where ionic liquid is covalently linked to silica domains. The morphology and the microstructure of the Si-IL xerogels were explored using NMR, SAXS and field emission scanning electron microscopy (FE-SEM). Cyclic voltammetry experiments were carried out to measure the apparent diffusion coefficient of the redox couple I−/I3− into these Si-IL gels. The diffusion coefficient of triiodide in the gel is comparable to the one observed in a solvent-free based ionic liquid electrolyte. These Si-IL gels were evaluated as electrolytes in quasi-solid-state DSSCs. For this purpose, various DSSCs have been fabricated. The cells containing Si-IL ionogels with 50 wt% of a silica modified liquid ionic precursor exhibit a short-circuit photocurrent of 2.8 mA cm−2, an open circuit voltage of 680 mV, a fill factor of 0.65, and an overall efficiency of 1.25%. Accordingly, this work constitutes a proof of concept. (10.1039/C3NJ01272G)
  DOI : 10.1039/C3NJ01272G
• Visible-emitting hybrid sol–gel materials comprising lanthanide ions: thin film behaviour and potential use as phosphors for solid-state lighting
  
  • Huang Xiaoguang
  • Zucchi Gaël
  • Tran Jacqueline
  • Pansu Robert B.
  • Brosseau Arnaud
  • Geffroy Bernard
  • Nief François
  Journal of new materials for electrochemical systems, Journal of New Materials for Electrochemical Systems; 1999, 2014, 38 (12), pp.5793-5800. The synthesis and characterization, as well as the film-forming and luminescent properties of four visible-emitting hybrid organic-inorganic sol-gel materials are reported. They show thermal stability up to 165°C. Deposition conditions were optimized to coat these materials as homogeneous and transparent thin films (~50 nm) with smooth surface, as probed by AFM. They were specifically designed to emit the primary colors. The blue-emitting material 1 was made up of a polyfluorene derivative embedded in a silica matrix, while the green (2) and red (3)-emissive materials comprise the TbIII and EuIII ions bound to the matrix, respectively. The films showed relatively high emission quantum yields efficiencies, with values of 19% (blue), 46% (green), and 21% (red). The three emitters were used to design a single emissive material (4) that showed emission colors from yellow-green to blue in a wide range of excitation wavelengths (254-380 nm). In particular, white light was obtained after excitation at 340 nm. (10.1039/C4NJ01110D)
  DOI : 10.1039/C4NJ01110D
• Multi-layer graphene obtained by high temperature carbon implantation into nickel films
  
  • Gutierrez G.
  • Le Normand F.
  • Muller D.
  • Aweke F.
  • Speisser C.
  • Antoni F.
  • Le Gall Y.
  • Lee C.
  • Cojocaru C.
  Carbon, Elsevier, 2014, 66, pp.1-10. (10.1016/j.carbon.2013.07.106)
  DOI : 10.1016/j.carbon.2013.07.106
• Growth mechanisms of carbon nanotrees with branched carbon nanofibers synthesized by plasma-enhanced chemical vapour deposition
  
  • He Zhanbing
  • Maurice Jean-Luc
  • Lee Chang Seok
  • Cojocaru Costel Sorin
  • Pribat D.
  CrystEngComm, Royal Society of Chemistry, 2014, 16, pp.2990. Y- and comb-type carbon nanotrees formed from branched carbon nanofibres grown by plasma-enhanced chemical vapour deposition were studied by transmission electron microscopy. Different growth mechanisms are proposed for the two types of nanotrees based on the observed and reconstituted dynamic transformations of the catalyst particles during synthesis. However, the splitting of the larger catalyst particles is required for both kinds of nanotrees, whatever the involved growth mechanism. The carbon nanotrees are well crystallized and connections of the branches are continuous, which may be interesting for future applications in nanoelectronic devices and also composite materials. (10.1039/C3CE42241K)
  DOI : 10.1039/C3CE42241K
• Dispositif d’acquisition, procédé de fabrication de celui-ci, procédé de mesure de force
  
  • Lebental Bérengère
  • Ghaddab Boutheina
  • Gaudefroy Vincent
  • Ruiz-Hitzky Eduardo
  • Aranda Pilar
  • Ruiz-Gracia Cristina
  • Henning Birger
  , 2014, pp.43p. L'invention concerne tout d’abord un transducteur permettant la détection et/ou la mesure de force lorsqu'il est intégré dans un capteur de force ; transducteur dans lequel la force appliquée n'est pas mesurée directement, mais est mesurée par l'intermédiaire d'une mesure de déformation : sous l’effet d'une force, le transducteur subit une déformation ; cette déformation induit une variation d'une grandeur mesurable du transducteur ; une partie de mesure du capteur détecte et/ou quantifie cette variation, et fournit un signal de sortie représentatif de la déformation et par suite de la force appliquée. Naturellement, un tel transducteur peut également être utilisé pour la détection ou la mesure de déformations. Une première application de tels transducteurs et capteurs est le pesage de véhicules sur une chaussée, à l'arrêt ou de préférence en mouvement. Quand un véhicule est sur une chaussée, à l’arrêt ou en mouvement, la chaussée se déforme localement sous ses pneus. Cette déformation, qui est fonction entre autres du poids du véhicule, peut être détectée et/ou mesurée par un capteur ou un réseau de capteurs. Cette ou ces informations de déformation peuvent alors être interprétées afin de détecter la présence et de déterminer le nombre de roues des véhicules présents ou circulant sur la chaussée, leur vitesse et/ou leur direction de déplacement, ou encore leur poids. Une deuxième application est le suivi de l’état de la chaussée, par exemple le suivi des déformations irréversibles de la chaussée et/ou la détection de fissures et/ou l’anticipation des fissures, par exemple en analysant la dérive des mesures du ou des capteurs soit obtenues en l’absence de véhicule soit agrégées suite au passage de plusieurs véhicules. Mots-clés : capteur de force, capteur de déformation, pesage en marche, nanoparticules
• Nanophotonics for ultrathin crystalline silicon photovoltaics: When photons (actually) meet electrons
  
  • Depauw V.
  • Abdo I.
  • Boukhicha R.
  • Cariou R.
  • Chen W.
  • Cosme I.
  • Deparis O.
  • Dmitriev A.
  • Drouard Emmanuel
  • El Daif Ounsi
  • Foldyna M.
  • Garcia-Caurel E.
  • Heidari B.
  • Herman A.
  • Lalouat Loic
  • Seassal Christian
  • Liu Jia
  • Lodewijks K.
  • Mandorlo Fabien
  • Orobtchouk Regis
  , 2014. no abstract
• 1,2-Dihydrophosphete: A Platform for the Molecular Engineering of Electroluminescent Phosphorus Materials for Light-Emitting Devices
  
  • Chen Hui
  • Pascal Simon
  • Wang Zuoyong
  • Bouit Pierre-Antoine
  • Wang Zisu
  • Zhang Yinlong
  • Tondelier Denis
  • Geffroy Bernard
  • Réau Régis
  • Mathey François
  • Duan Zheng
  • Hissler Muriel
  Chemistry - A European Journal, Wiley-VCH Verlag, 2014, 20 (31), pp.9784-9793. The discovery and molecular engineering of novel electroluminescent emitting materials is still a challenge in optoelectronics. In this work, we report on the development of new π-conjugated oligomers incorporating a dihydrophosphete skeleton. Variation of the substitution pattern of 1,2-dihydrophosphete derivatives and chemical modification of their P atoms afford thermally stable derivatives which are suitable emitters to construct organic light-emitting diodes. The optical and the electrochemical properties of these new P-based oligomers have been investigated in detail and are supported by DFT calculations. The OLED devices exhibit good performance and current independent CIE coordinates (10.1002/chem.201400050)
  DOI : 10.1002/chem.201400050
• Uniqueness of the differential Mueller matrix of uniform homogeneous media
  
  • Devlaminck Vincent
  • Ossikovski Razvigor
  Optics Letters, Optical Society of America - OSA Publishing, 2014, 39, pp.3149-3152. We show that the differential matrix of a uniform homogeneous medium containing birefringence may not be uniquely determined from its Mueller matrix, resulting in the potential existence of an infinite set of elementary polarization properties parameterized by an integer parameter. The uniqueness depends on the symmetry properties of a special differential matrix derived from the eigenvalue decomposition of the Mueller matrix. The conditions for the uniqueness of the differential matrix are identified, physically discussed and illustrated on examples from the literature.