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Based on the nonequilibrium Green's function formalism, we show a numerically efficient method to treat inelastic scattering in multidimensional atomistic codes. Using a simple rescaling approach, we detail the calculations of the lowest-order approximation (LOA) [Y. Lee et al., Phys. Rev. B 93, 205411 (2016)] series to the usual, computationally intensive, self-consistent Born approximation (SCBA). This, combined with the analytic continuation technique of Padé approximants, is applied to an atomistic code based on a tight-binding sp3d5s* model for electrons and holes, and a modified valence-force-field method for phonons [...]
> lire la suite de "Quantum treatment of phonon scattering for modeling of three-dimensional atomistic transport"
Rapid Communications Physical Review B95, 201412(R) (2017)
In the blooming field of on-surface synthesis, molecular building blocks are designed to self-assemble and covalently couple directly on a well-defined surface, thus allowing the exploration of unusual reaction pathways and the production of specific compounds in mild conditions. Here we report on the creation of functionalized organic nanoribbons on the Ag(110) surface. C–H bond activation and homo-coupling of the precursors is achieved upon thermal activation. The anisotropic substrate acts as an efficient template fostering the alignment of the nanoribbons, up to the full monolayer regime. [...]
> lire la suite de "On-surface synthesis of aligned functional nanoribbons monitored by scanning tunnelling microscopy and vibrational spectroscopy"
Nature Communications, overview article, 4 April 2017
Double rare earth tungstates NaCe(WO4)2 have been successfully synthesized hydrothermally for the first time with cerium as the trivalent cation in the tetragonal single phase. The resulting hierarchical superstructures were structurally characterized by X-ray diffraction in conjunction with Rietveld refinements and Raman spectroscopy. Their shape and size were observed by scanning and transmission electron microscopy coupled to energy dispersive spectroscopy. It was found that morphology modulation could be realized by controlling the amount of EDTA ligand (0.3–0.35 g) and the pH values (6–8) of the system solution. Hierarchical microstructures resulted firstly from the coalescence of nanosheets and secondly from the self-assembly of nanoplatelets, nanorods and nanosheets, giving rise to sphere, flower and novel spindle morphologies, respectively. [...]
> lire la suite de "Hierarchical design and control of
NaCe (WO4)2 crystals: structural and optical properties"

CrystEngComm, overview article, 15 July 2016
We report on a novel method for the implementation of core–shell SiGe-based nanocrystals combining silicon on insulator dewetting in a molecular beam epitaxy reactor with an ex situ Ge condensation process. With an in situ two-step process (annealing and Ge deposition) we produce two families of islands on the same sample: Si-rich, formed during the first step and, all around them, Ge-rich formed after Ge deposition. By increasing the amount of Ge deposited on the annealed samples from 0 to 18 monolayers, the islands' shape in the Si-rich zones can be tuned from elongated and flat to more symmetric and with a larger vertical aspect ratio. At the same time, the spatial extension of the Ge-rich zones is progressively increased as well as the Ge content in the islands. [...]
> lire la suite de "Fabrication of core–shell nanostructures via silicon on insulator dewetting and germanium condensation: towards a strain tuning method for SiGe-based heterostructures in a three-dimensional geometry"
Nanotechnology, overview article, 15 June 2016
Thin film dewetting can be efficiently exploited for the implementation of functionalized surfaces over very large scales. Although the formation of sub- micrometer sized crystals via solid-state dewetting represents a viable method for the fabrication of quantum dots and optical meta-surfaces, there are several limitations related to the intrinsic features of dewetting in a crystalline medium. Disordered spatial organization, size, and shape fluctuations are relevant issues not properly addressed so far. This study reports on the deterministic nucleation and precise positioning of Si- and SiGe-based nanocrystals by templated solid-state dewetting of thin silicon films. The dewetting dynamics is guided by pattern size and shape taking full control over number, size, shape, and relative position of the particles (islands dimensions and relative distances are in the hundreds nm range and fluctuate ≈11% for the volumes and ≈5% for the positioning) [...]
> lire la suite de "Templated Solid-State Dewetting of Thin Silicon Films"
Small, overview article, 17 November 2016
Pure and cobalt-doped zinc oxide aligned nanorods have been grown by the low-temperature (90 °C) aqueous chemical method on amorphous ZnO seed layer, deposited on a sapphire substrate. High crystallinity of these objects is demonstrated by the electron paramagnetic resonance investigation at liquid helium temperature. The successful incorporation of Co2+ ions in substitution of Zn2+ ones in the ZnO matrix has also been confirmed. A drastic reduction of intrinsic ZnO nanorods core defects is observed in the Co-doped samples, which enhances the structural quality of the NRs. The quantification of substitutional Co2+ ions in the ZnO matrix is achieved by comparison with a reference sample. The findings in this study indicate the potential of using the low-temperature aqueous chemical approach for synthesizing material for spintronics applications. [...]
> lire la suite de "EPR investigation of pure and Co-doped ZnO oriented nanocrystals"
Nanotechnology, overview article, 14 December 2016
We present a review of recent in situ experimentation studies of solidification front patterns and microstructures in alloys. Front-tracking diagnostics and real-time observation methods using high-resolution optical or X-ray imaging devices currently apply to model transparent systems as well as metallic alloys in thin and bulk samples. On a theoretical basis that spans the physics of nonequilibrium pattern formation and materials science, in combination with time-resolved numerical simulations, conclusive results of both fundamental- and applied-science interest have been obtained on major problems relative to multiscale microstructure selection, morphological transitions, and crystallographic effects during single- and multi-phase solidification. [...]
> lire la suite de "In situ observation of solidification patterns in diffusive conditions"
Acta Materiala, overview article, 15 April 2016
We report the fabrication of Si-based dielectric Mie resonators via a low cost process based on solid-state dewetting of ultra-thin amorphous Si on SiO2. We investigate the dewetting dynamics of a few nanometer sized layers annealed at high temperature to form submicrometric Si-particles. Morphological and structural characterization reveal the polycrystalline nature of the semiconductor matrix as well as rather irregular morphologies of the dewetted islands.[...]
> lire la suite de "Fabrication of poly-crystalline Si-based Mie resonators via amorphous Si on SiO2 dewetting"
Nanoscale, 8, 2844, 2016

Evénements

 

Réunion plénière du GDR Pulse
Paris, 2-4 octobre 2017

Reliability of Solar materials & Systems
Villa Méditerranée, Marseille, France, May 12th 2017

Conference on Advancements in Nuclear Instrumentation Measurements Methods and their Applications
Palais des Congres, Liège, Belgium June 19th to 23rd 2017

Ecole thématique du GDR CNRS Oxyfun
Caractérisations avancées des oxydes fonctionnels

Carry-le-Rouet, France, 25-30 septembre 2016

EDS 2016 18th International Conference on Extended Defects in Semiconductors
Les Issambres-St Aygulf, south of France, September 25-29, 2016

LaMoDy.1 School on Lattice and Molecular Dynamics Simulations of Materials
Girona, Spain, 19-23 september 2016

Conférence Nationale sur les Processus ULtimes d’épitaxie des SEmiconducteurs
Marseille, 18 - 22 juillet 2016

Ecole Franco-Marocaine de la Mesure et de l'Instrumentation Nucléaires EFMMIN4
Marseille, 18 au 21 juillet 2016

AFC 2016 - Congrès de l'Association Française de Cristallographie
Marseille, 4-7 juillet 2016

6th International Conference on NANOstructures and nanomaterials SElf-Assembly (NANOSEA)
Giardini Naxos (Me, Italy), July 3-8, 2016

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IM2NP - Unité Mixte de Recherche 7334 CNRS & Universités d'Aix-Marseille et de Toulon | adresse administrative : Faculté des Sciences Avenue Escadrille Normandie Niemen - Case 142 - 13397 Marseille Cedex 20 (France) | Directeur : R. Bouchakour | email : direction@im2np.fr | tel. +33 (0) 4 91 28 83 13

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