Activity Report 2010 - CNRS

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HIGHLIGHT : NANOMATERIALS, NANOASSEMBLY AND NANOSTRUCTURATION CONTACTS borsali@cermav.cnrs.fr FURTHER READING K. Aissou et al., Langmuir, 27 (7), pp 4098– 4103 (2011) C. Porto et al., Macromolecules, 44 (7), pp 2240–2244 (2011) NANOSTRUCTURED LIGHT-EMITTING SMALL MOLECULES VIA HYBRID NATURAL- BLOCK-SYNTHETIC SUPRAMOLECULAR ASSEMBLY Self-assembly is emerging as an elegant, 'bottom-up' method for fabricating nanostructured materials. As current polymers derive from petroleum - a resource that is being rapidly depleted - oligo and polysaccharides constitute an abundant, renewable, and yet undervalued resource for the fabrication of bio-inspired nanoelectronic devices. Within the framework of the 2007 RTRA project called “CELLULOSE HYBRID”, 3 laboratories (CERMAV, LTM and Léti) have conceived a new method to build a versatile hierarchical assembly of hybrid diblock copolymer (cellulose based material) which led to tunable-lightemitting films. (1 patent) Synthesis and self-assembly of glycopolymer-based copolymers in thin films First, the team designs a hybrid naturalblock-synthetic copolymer system where the synthetic block is polystyrene and the natural one is an amylose fragment: maltoheptaose (noted maltoheptaoseblock-polystyrene (Mal7-b-PS)) TEM pictures of Mal7-b-PS copolymer thin film confirm its phase organization (Fig. 1). They show a stripe pattern, with dark regions smaller than bright ones, caused by the orientation of MAL7 cylinders parallel to the film free surface. Fig. 1: TEM picture of Mal7-b-PS thin film showing a stripe pattern, with a lattice period of about 12 nm measured from FFT inset. Photoluminescence of lightemitting thin film For light-emitting applications, one important challenge is to fabricate thin films with an optimal structure i.e. having large interface area and domain size similar to the exciton diffusion length about 10 nm. It has been possible to fabricate supramolecular architecture with active 4’,4-bipyridine on maltoheptaose blocks which fits this requirement to get expected photonic properties. Photoluminescence (PL) data of Mal7(bipy) 1.0 -b-PS thin films deposited on SiO 2 substrate were recorded (Fig. 2) after different annealing times. It yields wellorganized films (48h annealing), exhibiting a three times higher PL signal compared to a poorly organized film (15 min annealing). Fig. 2: Photoluminescence spectra (excitation at 365 nm) of Mal7(bipy)1.0-b-PS thin film after 15 min (red) and 48h (black) annealing time. F ig.3: AFM phase image obtained from Mal7(bipy)1.0-b-PS thin film. The phase crosssection profile of the continuous red line on the AFM phase image inset revealed a distance of 11nm between two white spots. This innovative conception of organic light-emitting diodes (OLEDs) has been patented (French patent deposited in <strong>2010</strong>). 9
CRISTAL PHASE TRANSITIONS IN PRESSURIZED SILICON NANOWIRES The possibility to synthesize new crystalline phases in single silicon nanowires recently attracted attention owing to the potential tuning of the opto electronic properties that can be expected when the crystal structure undergoes phase transitions. In particular, it is predicted that the wurtzite phase which is metastable at room pressure and temperature is an indirect semiconductor with a 0.85 eV band gap. Unlike most of its III-V compounds counterparts where axial phase switching between cubic and hexagonal structure is routinely observed, direct crystal growth and characterization of wurtzite silicon nanowires is still a challenging task. In the frame of the NEP-IV project, we initiated a structural study of phase transitions in Si NWs, based on a “pressure engineering” approach that uses diamond (phase I) Si NWs as a starting material instead of the direct synthesis of modified wires, still under controversy. Indeed, in the case of bulk material, it was shown in the 60’s and 70’s that a highpressure loading and unloading cycle leads to high-pressure intermediate metallic or semimetallic phases that relax upon pressure release into the metastable Si III phase (body centred cubic, semimetallic) and Si IV phase (wurtzite, semiconductor) under a slight annealing of Si III at room pressure. In our experiment, we used a diamond-anvil cell to monitor the pressure-induced phase changes, which we followed by confocal micro-Raman spectroscopy. Size calibrated Si NWs were synthesized using 50 nm gold colloids as seeds for the vapour liquid solid growth. The sample was sonicated in a 4:1 methanol-ethanol mixture and the resulting enriched solution was drop casted in the pressure cell for Raman investigation. This resulted in the formation of visible Si NW bundles at some preferential places in the cell that permitted precise excitation of the same group of wires all along the pressure rise and release cycle. The results are reported in Fig. 1 and show the characteristic Stokes Raman spectrum observed in bulk silicon I under increasing hydrostatic pressures up to 16-18 GPa where a first phase transition occurs, presumably towards the Si II phase (body centred tetragonal, metallic), which has no sharp Raman response. After completion of the phase transition and transformation of all Si I into Si II, pressure is progressively released. This does not lead to Si I phase retrieval but instead, and like in the bulk material, Si II remains stable down to the 5-10 GPa range where a phase transition towards Si III phase takes place. The characteristic Raman peaks of Si III are detected together with two broader bands corresponding to amorphous Si but no contribution from Si I is found. Upon aperture of the cell, as the pressure is fully released to room pressure, the alcohol evaporates and Si I phase is immediately recovered, without any transit via Si IV. This is most likeky due to the lack of heat sink in the wire surroundings and subsequent intense laser annealing of Si III. Further experiments are necessary to fully understand the diameter dependence of the phase transitions and special care will be given to the low-pressure domain upon pressure release where observation of the Si IV phase is expected. Fig. 1: Raman spectra obtained on a bundle of 50 nm diameter Si NWs for increasing pressures (top) and decreasing pressures (bottom). The different phases are labeled I, II and III CONTACTS nicolas.pauc@cea.fr pierre.bouvier@grenoble-inp.fr mael.guennou@grenoble-inp.fr 10 HIGHLIGHT : NANOMATERIALS, NANOASSEMBLY AND NANOSTRUCTURATION
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Date of publication: May 2011 We wo
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Nanosciences Foundation Activity Re
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Part I: ACHIEVEMENTS & PROSPECTS Th
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THE NANOSCIENCES FOUNDATION AT THE
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OUTSTANDING BENEFITS CATALYZED BY T
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The laureates of the 2010 Chairs of
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‘Mobilité d’Excellence’: a n
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INTEGRATION ON SITE BETWEEN BASIC R
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OVERVIEW Fig.3: LANEF framework. Ba
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The Nanosciences Foundation budget
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The evolution of the funding progra
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OVERVIEW Fig. 6: Total number of vi
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ACKNOWLEDGEMENTS One couldn’t fin
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Part II: SCIENTIFIC REPORT 1 - QUAN
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1 - QUANTUM NANOELECTRONICS Moore
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Core/shell nanowires: conductance C
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2 - NANOMAGNETISM AND SPINTRONICS B
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than 10 8 V/m and to compare this t
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sites. The calculations indicate th
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3 - NANOPHOTONICS The optical prope
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Cavity-feeding : decoherence as a r
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4 - MOLECULAR ELECTRONICS Molecular
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5 - NANOMATERIALS, NANOASSEMBLY AND
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Phase-change memory RTRA Project 20
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6 - NANO- CHARACTERISATION AND NANO
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when compared, for example, to the
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7 - NANO APPROACHES TO LIFE SCIENCE
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Innovative biochips to detect and s
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Implantable brain computer interfac
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8 - NANOMODELING, THEORY & SIMULATI
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Growth, patterning, defects & struc
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9 - TECHNOLOGICAL FACILITIES Create
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CRG: The French Cooperative Researc
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The Numerical Simulation Facility T
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10 - EDUCATION AND SCIENTIFIC ANIMA
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Q-NET: a new European Initial Train
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Thesis Prize Award Ceremonies 2009
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2010 Speaker From Date Title Resear
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Workshop “Super Resolution Optica
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Workshop “Electronic Noise and Re
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Workshop « New trends in Electrica
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List of the Quantum Nanoelectronics
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Hélène LE SUEUR Laboratoire de Ph
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Quantum Nanoelectronics Seminars in
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Invitations to talk at seminars: "
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- Anton ANDREEV (University of Wash
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Cellulose Hybrid block copolymers /
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PART 3 S. J. C. Yates, J. J. A. Bas
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D. A. Stewart, I. Savic, and N. Min
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DISPOGRAPH / RTRA project Post-doct
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2009 Call for Proposals MUSCADE Cha
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Piotr Laczkowski, Danny Hykel, Serg
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Part IV: SUPPLEMENTS Appendix 1: th
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Appendix 2: the Foundation’s boar
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Appendix 4: the Steering Committee
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RTRA projects support Major topic A
Page 120 and 121: Appendix 6: 2010 Call for Proposals
Page 122 and 123: Education and Scientific Animation
Page 124 and 125: 2008 Call for Proposals Name Nation
Page 126 and 127: Appendix 8: List of the Post Doc Fe
Page 128 and 129: Appendix 9: List of the PhD student
Page 130 and 131: PhD students supported in 2010 Name
Page 132 and 133: Appendix 11: List of the Reviewers
Page 134 and 135: 2010 Call for Proposals Reviewer La
Page 136 and 137: Nom du laboratoire Département de
Page 138 and 139: Nom du laboratoire GRENOBLE INSTITU
Page 140 and 141: Nom du laboratoire Institut de Micr
Page 142 and 143: Nom du laboratoire Institut Fourier
Page 144 and 145: Nom du laboratoire Institut Néel I
Page 146 and 147: Nom du laboratoire Laboratoire d'In
Page 148 and 149: Nom du laboratoire Laboratoire de P
Page 150 and 151: SUPPLEMENTS 5 : Très nombreuses vi
Page 152 and 153: Nom du laboratoire Laboratoire Inte
Page 154 and 155: Nom du laboratoire Laboratoire Nati
Page 156 and 157: Nom du laboratoire Techniques de l
Page 158 and 159: SUPPLEMENTS 48
Page 160: HIGHLIGHTS QUANTUM NANOELECTRONICS:
Page 163 and 164: FIB NANO- TOMOGRAPHY OF DEFECTS IN
Page 165 and 166: DETECTING SINGLE NANOPARTICLE MAGNE
Page 167 and 168: QUANTUM HETEROSTRUCTURES IN II-VI N
Page 169: ELECMOL’10 CONFERENCE An importan
Page 173 and 174: SCANNING GATE NANOELECTRONICS In th
Page 175 and 176: CONTROL OF THERMAL CONDUCTIVITY AT
Page 178 and 179: Roland HERINO (past Director) Jean-
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