Publications

2011

• High-quality single-walled carbon nanotubes synthesis by hot filament CVD on Ru nanoparticle catalyst
  
  • Bouanis Fatima
  • Baraton Laurent
  • Huc Vincent
  • Pribat Didier
  • Cojocaru Costel
  Thin Solid Films, Elsevier, 2011, 519 (14), pp.4594-4597. (10.1016/j.tsf.2011.01.326)
  DOI : 10.1016/j.tsf.2011.01.326
• Capacitive behavior of pentacene-based diodes: Quasistatic dielectric constant and dielectric strength
  
  • Kim Chang Hyun
  • Yaghmazadeh Omid
  • Tondelier Denis
  • Bin Jeong Yong
  • Bonnassieux Yvan
  • Horowitz Gilles
  Journal of Applied Physics, American Institute of Physics, 2011, 109, pp.083710. The capacitive behavior of pentacene films was investigated in the metal-semiconductor-metal (MSM) diode structure. Impedance analysis of diodes with a thick pentacene layer up to 1012 nm showed a full depletion of the organic layer. This observation allowed us to regard the MSM diode as a parallel-plate capacitor in the reverse-bias regime without current flow. Under forward-bias, the diode was evaluated through frequency-dependent impedance measurements by using an equivalent circuit composed of a single parallel resistance-capacitance circuit. The analysis of the data in both the reverse and forward bias regime led us to electrical methods for quantifying dielectric properties of pentacene.
• Thin crystalline silicon solar cells based on epitaxial films grown at 165 °C by RF-PECVD
  
  • Cariou Romain
  • Labrune Martin
  • Roca I Cabarrocas Pere
  Solar Energy Materials and Solar Cells, Elsevier, 2011, 95 (8), pp.2260-2263. We report on heterojunction solar cells whose thin intrinsic crystalline absorber layer has been obtained by plasma enhanced chemical vapor deposition at 165 °C on highly doped p-type (1 0 0) crystalline silicon substrates. We have studied the effect of the epitaxial intrinsic layer thickness in the range from 1 to 2.5 μm. This absorber is responsible for photo-generated current whereas highly doped wafer behave like electric contact, as confirmed by external quantum efficiency measurements and simulations. A best conversion efficiency of 7% is obtained for a 2.4 μm thick cell with an area of 4 cm2, without any light trapping features. Moreover, the achievement of a fill factor as high as 78.6% is a proof that excellent quality of the epitaxial layers can be produced at such low temperatures. (10.1016/j.solmat.2011.03.038)
  DOI : 10.1016/j.solmat.2011.03.038
• Nanosensors for structural monitoring in civil engineering: New insight on promising carbon nanotubes devices
  
  • Lebental Bérengère
  • Norman Evgeny
  • Gorintin Louis
  • Renaux Philippe
  • Bondavalli Paulo
  • Cojocaru Costel-Sorin
  • Ghis Anne
  , 2011. In recent years, requirements in terms of service-life of civil engineering structures have become more and more stringent, so that the focus of designers and owners is now set on structural durability. Foreseeing structural failures and repairing damaged structures at an early stage has become a major stake. This approach calls for an accurate knowledge of the state of the structure at any point in its lifetime. This is the incentive for the world-wide development of various in-situ monitoring techniques for structural materials. However, by measuring global structural quantities only, the existing monitoring techniques provide only indirect information on the structural health of the structure.
• Geometrical optimization and electrical performance comparison of thin-film tandem structures based on pm-Si:H and µc-Si:H using computer simulation
  
  • Dadouche Foudil
  • Bethoux Olivier
  • Gueunier-Farret Marie-Estelle
  • Johnson Erik
  • Roca I Cabarrocas Pere
  • Marchand C.
  • Kleider Jean-Paul
  EPJ Photovoltaics, EDP sciences, 2011, 2, pp.20301. This article investigates the optimal efficiency of a photovoltaic system based on a silicon thin film tandem cell using polymorphous and microcrystalline silicon for the top and bottom elementary cells, respectively. Two ways of connecting the cells are studied and compared: (1) a classical structure in which the two cells are electrically and optically coupled; and (2) a new structure for which the "current-matching" constraint is released by the electrical decoupling of the two cells. For that purpose, we used a computer simulation to perform geometrical optimization of the studied structures as well as their electrical performance evaluation. The simulation results show that the second structure is more interesting in terms of efficiency. (10.1051/pvd/2011001)
  DOI : 10.1051/pvd/2011001
• Anisotropy coefficients of a Mueller matrix
  
  • Arteaga Oriol
  • Garcia-Caurel Enric
  • Ossikovski Razvigor
  Journal of the Optical Society of America. A Optics, Image Science, and Vision, Optical Society of America, 2011, 28 (4), pp.548. Anisotropy coefficients α, β, and γ that describe the type and the relative amount of the three kinds of anisotropy generally present in a Mueller matrix are introduced. Their derivation, algebraic properties, and physical interpretation are discussed. In particular, they are shown to permit a geometrical representation for the anisotropy and polarizing characteristics of a Mueller matrix. Illustrative experimental examples are provided.
• The Utility of 2,2'-bipyrimidine in Lanthanide Chemistry: From Materials Synthesis to Structural and Physical Properties
  
  • Zucchi Gaël
  International journal of inorganic chemistry, 2011, 2011, pp.Article ID 918435. This paper reviews the recent investigations undertaken on the use of 2,2'-bipyrimidine (bpm) as a ligand for designing molecular complexes as well as polymeric lanthanide materials. A special emphasis is put on the ability of this polydentate neutral ligand to yield compounds of various dimensionalities, to act as a connector between these large ions and influence their emissive and magnetic properties. This ligand can adopt a terminal or a bridging coordination mode with lanthanide ions, thus generating a wealth of frameworks of various topologies with the 4f elements. The main focus of this review is to show the originality brought by bpm in lanthanide structural chemistry and solid state photophysics and magnetism. (10.1155/2011/918435)
  DOI : 10.1155/2011/918435
• Mueller matrix ellipsometry of artificial non-periodic line edge roughness in presence of finite numerical aperture
  
  • Foldyna Martin
  • Germer Thomas A.
  • Bergner Brent C.
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2011, 7971, pp.19. We used azimuthally-resolved spectroscopic Mueller matrix ellipsometry to study a periodic silicon line structure with and without artificially-generated line edge roughness (LER). The unperturbed, reference grating profile was determined from multiple azimuthal configurations using a generalized ellipsometer, focusing the incident beam into a 60 μm spot. We used rigorous numerical modeling, taking into account the finite numerical aperture, introducing significant depolarization effects, and determining the profile shape using a four trapezoid model for the line profile. Data obtained from the artificially perturbed grating were then fit using the same model, and the resulting root-mean-square error (RMSE) values for both targets were compared. The comparison shows an increase in RMSE values for the perturbed grating that can be attributed to the effects of LER. (10.1117/12.879518)
  DOI : 10.1117/12.879518
• Molecular Arrangement in Self-Assembled Azobenzene-Containing Thiol Monolayers at the Individual Domain Level Studied through Polarized Near-Field Raman Spectroscopy
  
  • Chaigneau Marc
  • Picardi Gennaro
  • Ossikovski Razvigor
  International Journal of Molecular Sciences, MDPI, 2011, 12, pp.1245. 6-[4-(phenylazo)phenoxy]hexane-1-thiol self-assembled monolayers deposited on a gold surface form domain-like structures possessing a high degree of order with virtually all the molecules being identically oriented with respect to the surface plane. We show that, by using polarized near-field Raman spectroscopy, it is possible to derive the Raman scattering tensor of the ordered layer and consequently, the in-plane molecular orientation at the individual domain level. More generally, this study extends the application domain of the near-field Raman scattering selection rules from crystals to ordered organic structures. (10.3390/ijms12021245)
  DOI : 10.3390/ijms12021245
• Characterization of silicon heterojunctions for Solar Cells
  
  • Kleider Jean-Paul
  • Alvarez José
  • Labrune Martin
  • Roca I Cabarrocas Pere
  • Maslova Olga Alexandrovna
  • Favre Wilfried
  • Gueunier-Farret Marie-Estelle
  Nanoscale Research Letters, SpringerOpen, 2011, 6, pp.152. Conductive-probe atomic force microscopy (CP-AFM) measurements reveal the existence of a conductive channel at the interface between p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) as well as at the interface between n-type a-Si:H and p-type c-Si. This is in good agreement with planar conductance measurements that show a large interface conductance. It is demonstrated that these features are related to the existence of a strong inversion layer of holes at the c-Si surface of (p) a-Si:H/(n) c-Si structures, and to a strong inversion layer of electrons at the c-Si surface of (n) a-Si:H/(p) c-Si heterojunctions. These are intimately related to the band offsets, which allows us to determine these parameters with good precision. (10.1186/1556-276X-6-152)
  DOI : 10.1186/1556-276X-6-152
• Evidence for the formation of two phases during the growth of SrTiO3 on silicon
  
  • Niu G.
  • Penuelas J.
  • Largeau L.
  • Vilquin B.
  • Maurice J.-L.
  • Botella C.
  • Hollinger G.
  • Saint-Girons G.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2011, 83, pp.054105. Epitaxial SrTiO3 (STO)/Si templates open a unique opportunity for the integration of ferroelectric oxides, such as BaTiO3 on silicon and for the realization of new devices exploiting ferroelectricity. STO itself has been shown as ferroelectric at room temperature when deposited in thin layers on Si, while bulk STO is tetragonal and, thus, ferroelectric below 105 K. Here, we demonstrate the coexistence, at room temperature, of strained cubic and tetragonal phases in thin STO/Si layers. The tetragonal STO phase presents a pronounced tetragonality for thicknesses up to 24 ML. Above this thickness, the strained cubic STO phase starts relaxing while the tetragonal STO phase progressively transits to cubic STO. The origin of the simultaneous formation of these two phases is analyzed and is attributed to oxygen segregation at the early stages of the growth. (10.1103/PhysRevB.83.054105)
  DOI : 10.1103/PhysRevB.83.054105
• Carbon nanotube based humidity sensor
  
  • Norman Evgeny
  • Gorintin Louis
  • Lebental Bérengère
  • Bondavalli Paulo
  • Cojocaru Costel-Sorin
  , 2011.
• Apport de la 2,2'-bipyrimidine à la chimie structurale et aux propriétés physiques des matériaux hybrides formés avec les éléments f
  
  • Zucchi Gaël
  , 2011.
• Etchant-induced shaping of nanoparticle catalysts during chemical vapour growth of carbon nanofibres
  
  • He Z. B.
  • Maurice Jean-Luc
  • Lee C. S.
  • Gohier A.
  • Legagneux P.
  • Pribat D.
  • Cojocaru C. S.
  Carbon, Elsevier, 2011, 49, pp.435. Carbon nanofibres (CNFs) obtained by plasma enhanced chemical vapour deposition are made of cone-shaped graphene layers, the opening angle of which has a significant influence on their properties: the smaller the angle, the closer the properties to those of carbon nanotubes. That angle is determined by the shape of the metal nanoparticle used to catalyse the growth. We show in this paper that the shape of Ni nanoparticle catalysts, and in turn the CNF properties, can be tuned during plasma-enhanced chemical vapour deposition, by the choice of the etchant gas. We show in particular that a water-containing etchant (H2O or H2O+H2) increases the growth rate by an order of magnitude at 600°C compared to an ammonia-containing etchant (NH3 or NH3+H2), and leaves more elongated Ni particles with a cone angle three times smaller. We conclude that the cone angle and the growth rate are directly related, and propose a mechanism to explain that large difference between the two etchants. (10.1016/j.carbon.2010.09.040)
  DOI : 10.1016/j.carbon.2010.09.040
• Optimization of organized silicon nanowires growth inside porous anodic alumina template using hot wire chemical vapor deposition process
  
  • Lefeuvre E.
  • Kim K.H.
  • Maurice J.-L.
  • Châtelet Marc
  • Pribat D.
  • Cojocaru C.S.
  Thin Solid Films, Elsevier, 2011, 519, pp.4603. A Hot Wire assisted Chemical Vapor Deposition (HWCVD) process has been developed for producing highdensity arrays of parallel, straight and organized silicon nanowires (SiNWs) inside vertical Porous Anodic Alumina (PAA) templates, exploring temperatures ranging from 430 °C to 600 °C, and pressures varying between 2.5 and 7.5 mbar. In order to prevent parasitic amorphous silicon (a-Si) deposit and to promote the crystalline SiNWs growth, we used a tungsten hot wire to partially crack H2 into atomic hydrogen, which acts like a selective etchant regarding a-Si. Here we describe the optimization route we followed to limit the deposit of a-Si onto the surface of the porous membrane and on the walls of the pores, which led to the possibility to grow SiNWs inside the PAA membranes. Such an approach has high potentialities for device realization, like PIN junctions, FETs or electrodes for Li-ion batteries. (10.1016/j.tsf.2011.01.333)
  DOI : 10.1016/j.tsf.2011.01.333
• Generalized ellipsometry of artificially designed line width roughness
  
  • Foldyna Martin
  • Germer Thomas A.
  • Bergner Brent C.
  • Dixson Ronald G.
  Thin Solid Films, Elsevier, 2011, 519, pp.2633-2636. We use azimuthally resolved spectroscopic Mueller matrix ellipsometry to study a periodic silicon line structure with and without artificially-generated line width roughness (LWR). We model the artificially perturbed grating using one- and two-dimensional rigorous coupled-wave methods in order to evaluate the sensitivity of the experimental spectrally resolved data, measured using a generalized ellipsometer, to the dimensional parameters of LWR. The sensitivity is investigated in the context of multiple conical mounting (azimuth angle) configurations, providing more information about the grating profile. (10.1016/J.TSF.2010.11.085)
  DOI : 10.1016/J.TSF.2010.11.085
• Conductive-probe atomic force microscopy characterization of silicon nanowires
  
  • Alvarez José
  • Ngo Irène
  • Gueunier-Farret Marie-Estelle
  • Kleider Jean-Paul
  • Yu Linwei
  • Roca I Cabarrocas Pere
  • Rouvière Emmanuelle
  • Celle Caroline
  • Mouchet Céline
  • Simonato Jean-Pierre
  Nanoscale Research Letters, SpringerOpen, 2011, 6, pp.110. The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated. (10.1186/1556-276X-6-110)
  DOI : 10.1186/1556-276X-6-110
• Optimized network of multi-walled carbon nanotubes for chemical sensing
  
  • Gohier A.
  • Chancolon Jérôme
  • Chenevier P.
  • Porterat D.
  • Mayne-L'Hermite M.
  • Reynaud C.
  Nanotechnology, Institute of Physics, 2011, 22 (10), pp.105501. This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbon nanotubes (MWCNTs) grown by aerosol-assisted chemical vapour deposition. The sensor sensitivity was optimized using chlorine as analyte by tuning both CNT network morphology and CNT electronic properties. Optimized devices, operating at room temperature, have been calibrated over a large range of concentration and are shown to be sensitive down to 27 ppb of chlorine. The as-grown MWCNT response is compared with responses of 2000 degrees C annealed CNTs, as well as of nitrogen-doped CNTs and CNTs functionalized with polyethyleneimine (PEI). Under chlorine exposure, the resistance decrease of as-grown and annealed CNTs is attributed to charge transfer from chlorine to CNTs and demonstrates their p-type semiconductor behaviour. XPS analysis of CNTs exposed to chlorine shows the presence of chloride species that confirms electron charge transfer from chlorine to CNTs. By contrast, the resistance of nitrogen-doped and PEI functionalized CNTs exposed to chlorine increases, in agreement with their n-type semiconductor nature. The best response is obtained using annealed CNTs and is attributed to their higher degree of crystallinity. (10.1088/0957-4484/22/10/105501)
  DOI : 10.1088/0957-4484/22/10/105501
• Towards a realistic numerical modeling of polarimetric response of healthy and pathological colon tissue
  
  • Antonelli Maria Rosaria
  • Pierangelo Angelo
  • Novikova Tatiana
  • Validire Pierre
  • Benali Abdelali
  • Gayet Brice
  • Martino Antonello De
  , 2011, pp.80872U. (10.1364/ECBO.2011.80872U)
  DOI : 10.1364/ECBO.2011.80872U
• All-printed infrared sensor based on multiwalled carbon nanotubes
  
  • Gohier Aurelien
  • Dhar Anirban
  • Gorintin Louis
  • Bondavalli Paolo
  • Bonnassieux Yvan
  • Cojocaru Costel Sorin
  Applied Physics Letters, American Institute of Physics, 2011, 98, pp.063103. This contribution deals with all-printed infrared sensors fabricated using multiwalled carbon nanotubes deposited on a flexible polyimide substrate. A high responsivity of up to 1.2 kV/W is achieved at room temperature in ambient air. We evidence a strong dependence of the device transduction mechanism on the surrounding atmosphere, which can be attributed to bolometric effect interference with water molecule desorption upon irradiation. (10.1063/1.3552686)
  DOI : 10.1063/1.3552686
• Stability and evolution of low-surface-tension metal catalyzed growth of silicon nanowires
  
  • Yu L.W
  • Fortuna F.
  • O'Donnell B.
  • Patriache G.
  • Roca I Cabarrocas Pere
  Applied Physics Letters, American Institute of Physics, 2011, 98, pp.123113. Low-surface-tension metals were predicted to be insufficient to catalyze the growth of silicon nanowires (SiNWs) in vapor-liquid-solid (VLS) mode while counter examples do exist, for example, in the tin-or indium-catalyzed SiNWs. This puzzle remains largely unresolved. We first examine the local tension-force-balance in a tin-catalyzed SiNW by using a cross-section analysis. We found that the existence of an ultrathin sidewall-spreading catalyst layer helps to stabilize the catalyst drop during growth. The predicted contact-angle evolution, by an energetic balance model, is also supported by the experimental data. These results bring critical understanding on the low-surface-tension catalyzed VLS process (10.1063/1.3569817)
  DOI : 10.1063/1.3569817
• Ex-vivo characterization of human colon cancer by Mueller polarimetric imaging
  
  • Pierangelo Angelo
  • Benali Abdelali
  • Antonelli Maria Rosaria
  • Novikova Tatiana
  • Validire Pierre
  • Gayet Brice
  • de Martino Antonello
  Optics Express, Optical Society of America - OSA Publishing, 2011, 19 (2), pp.1582-1593. Cancerous and healthy human colon samples have been analyzed ex-vivo using a multispectral imaging Mueller polarimeter operated in the visible (from 500 to 700 nm) in a backscattering configuration with diffuse light illumination. Three samples of Liberkuhn colon adenocarcinomas have been studied: common, mucinous and treated by radiochemotherapy. For each sample, several specific zones have been chosen, based on their visual staging and polarimetric responses, which have been correlated to the histology of the corresponding cuts. The most relevant polarimetric images are those quantifying the depolarization for incident linearly polarized light. The measured depolarization depends on several factors, namely the presence or absence of tumor, its exophytic (budding) or endophytic (penetrating) nature, its thickness (its degree of ulceration) and its level of penetration in deeper layers (submucosa, muscularis externa and serosa). The cellular density, the concentration of stroma, the presence or absence of mucus and the light penetration depth, which increases with wavelength, are also relevant parameters. Our data indicate that the tissues with the lowest and highest depolarizing powers are respectively mucus-free tumoral tissue with high cellular density and healthy serosa, while healthy submucosa, muscularis externa as well as mucinous tumor probably feature intermediate values. Moreover, the specimen coming from a patient treated successfully with radiochemotherapy exhibited a uniform polarimetric response typical of healthy tissue even in the initially pathological zone. These results demonstrate that multi-spectral Mueller imaging can provide useful contrasts to quickly stage human colon cancer ex-vivo and to distinguish between different histological variants of tumor. (10.1364/OE.19.001582)
  DOI : 10.1364/OE.19.001582
• Impact of model parameters on Monte Carlo simulations of backscattering Mueller matrix images of colon tissue
  
  • Antonelli Maria Rosaria
  • Pierangelo Angelo
  • Novikova Tatiana
  • Validire Pierre
  • Benali Abdelali
  • Gayet Brice
  • de Martino Antonello
  Biomedical optics express, Optical Society of America - OSA Publishing, 2011, 2 (7), pp.1836-1851. (10.1364/BOE.2.001836)
  DOI : 10.1364/BOE.2.001836
• Laterally organized carbon nanotube arrays based on hot-filament chemical vapor deposition
  
  • Kim Ki Hwan
  • Lefeuvre Emmanuel
  • Châtelet Marc
  • Pribat Didier
  • Cojocaru Costel Sorin
  Thin Solid Films, Elsevier, 2011, 519, pp.4598-4602. Lateral porous anodic alumina (PAA) templates were used to organize carbon nanotubes (CNTs) grown by a hot-filament assisted chemical vapor deposition (HFCVD) process. For the CNT growth, we used a modified "home-made" HFCVD system with two independently powered filaments which are fitted respectively on the methane (CH4) gas line, which serves as a carbon precursor and on the hydrogen (H2) gas line, which acts as an etching agent for the parasitic amorphous carbon. Various activation powers of the hot filaments were used to directly or indirectly decompose the gas mixtures at relatively low substrate temperatures. A parametric study of the HFCVD process has been carried out for optimizing the confined CNTs growth inside the lateral PAA templates. (10.1016/j.tsf.2011.01.334)
  DOI : 10.1016/j.tsf.2011.01.334
• Real-time in situ Mueller matrix ellipsometry of GaSb nanopillars: observation of anisotropic local alignment
  
  • Nerbo Ingar Stian
  • Le Roy Sébastien
  • Foldyna Martin
  • Sondergard Elin
  • Kildemo Morten
  Optics Express, Optical Society of America - OSA Publishing, 2011, 19 (13), pp.12551-12561. The formation of GaSb nanopillars by low energy ion sputtering is studied in real-time by spectroscopic Mueller matrix ellipsometry, from the initial formation in the smooth substrate until nanopillars with a height of 200 - 300 nm are formed. As the nanopillar height increased above 100 nm, coupling between orthogonal polarization modes was observed. Ex situ angle resolved Mueller polarimetry measurements revealed a 180 degrees azimuth rotation symmetry in the off-diagonal Mueller elements, which can be explained by a biaxial material with different dielectric functions epsilon(x) and epsilon(y) in a plane parallel to the substrate. This polarization coupling can be caused by a tendency for local direction dependent alignment of the pillars, and such a tendency is confirmed by scanning electron microscopy. Such observations have not been made for GaSb nanopillars shorter than 100 nm, which have optical properties that can be modeled as a uniaxial effective medium (10.1364/OE.19.012551)
  DOI : 10.1364/OE.19.012551