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A2 : INORGANIC NANO-MATERIALS
Article mis en ligne le 11 décembre 2017
dernière modification le 10 janvier 2018
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Axe A : ELECTRONIC STRUCTURE-BASED FUNCTIONAL MATERIALS

A2 : Inorganic Nano-materials

 

Due to their extremely small dimensions and their related chemical (specific area, reactivity...) physical (magnetic relaxation, quantum confinement...) properties, electronic-structure based functional nanomaterials are the basis of newly emerging nanotechnologies for various device applications and are also at the origin of very fruitful fundamental research. The capabilities for the design, fabrication and study of nanoscale materials, with an emphasis on atomic-level tailoring to achieve desired properties and functions around their electronic structure, are highly exciting challenges.

The sub-axis "inorganic nanomaterials" of the SEAM labex concerns a variety of materials, namely oxydes, semiconductors, metals, which are studied at the nanoscale from 1 nm to 100 nm. The objectives are to make a link between the structure of the nanomaterials (ultra-thin layers, quantum boxes, nanoparticles) and their physical properties (electronic, magnetic and optical), including also superconductivity, photonics, multiferroïcity. The ultimate goal is to elaborate new devices from these new functionalities. For information storage and telecommunications applications, the SEAM teams (MPQ, ITODYS, MSC, and LSPM will study of the magnetic properties of nanomagnets with a special emphasis on the interplay between intrinsic properties arising from their finite size and collective effects due to the different kinds of interactions between them.

Their objectives are first to produce original nanostructures by chemical or physical routes as powders, thin films supported nanodots, magnetically contrasted nanocomposites or metamaterials, hybrid architectures obtained by controlled aggregation of magnetic nanoparticles, nanostructured bulk metals and ceramics obtained by spark plasma sintering. They also aim at measuring the magnetic properties of these new materials, both in the low frequency (a few Hz) and very high frequency (up to 20 GHz) regimes. Low frequency hysteresis cycles or dynamical susceptibilities are determined by either SQUID or magneto-optical measurements. The goal is to extract key quantities like the magnetic anisotropy for original nanomagnets and to understand the mechanisms of thermal reversal which is a scientific bottleneck (superparamagnetic limit) in the storage industry. Recent results show that the low frequency reversal is strongly influenced by the high frequency spin-wave modes inside the nanomaterials. For biomedical applications, the project is based on the ITODYS and MPQ skills in magnetic nanoparticles synthesis, their surface coating make them biocompatible, specific (targeting) and/or sensitive (to pH, temperature, pressure, ionic strength, light, electrical signal, magnetic field, or specific biomolecular interactions ...) and the study of their magnetic and magneto-mechanic behavior under in vivo operating conditions.

The ultimate goal is to propose biogenic smart multifunctional nano-tools able to perform, at the same time, several tasks from detection to therapy. These nano-tools can be magnetic hydrogels, vesicles, or just simple hybrid nanoparticles, which will therefore be capable of performing several biomedical tasks in a living body and possess biological functionalities devoted to biochemical/biological recognition. The large available facilities offered by the SEAM Labex are also a token of high level research in Multiferroic nanomaterials
Most materials still display relatively weak coupling between electric and magnetic order which can be a drawback for the development of multiferroic based devices. From a more fundamental point of view the current understanding of the magneto-electrical coupling is still sketchy at best. The SEAM teams (ITODYS, MPQ, LSPM) plan to adopt two strategies, an intrinsic approach based on the elaboration and the study of pseudo single crystals (epitaxial thin films) and an extrinsic one based on the preparation of granular nanocomposites by the integration of magnetic nanoparticles inside a ferroelectric polymer or the fabrication of ultra-thin heteronanostructures using Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), or physical vapor deposition (PVD) films growth techniques and the study of the order coupling. In parallel, the involved teams aim at developing new nanoscale probes such as non-standard near-field microscopy and microstripes-ferromagnetic resonance (FMR) techniques which will allow the study of local magnetization/polarization distribution in the ferromagnetic/ferroelectric nano-systems under the application of magnetic/electric field. Analyzing the near-field microscopy images and the detected electric signal, we’ll study the dynamics of the ferroelectric and ferromagnetic domains and hysteresis loops of these domains, at the nanoscale level, under the application of a magnetic/electric field. An exciting prospect (magnonics) in the field of spintronics is to use the wave like excitations of a magnetic material as a means of transmitting and processing information. Like spintronics, the key goal of magnonics is to read/write non-volatile spin information with minimal or no energy consumption. With wavelengths much shorter than EM waves, spin waves are suitable for the miniaturization of fast devices operating from gigahertz to terahertz frequencies. Hence, magnonic devices can be combined with microwave electronics and photonics technologies. Multiferroic materials could lead to electrical control of magnetic effects and vice-versa. Photonic nano-materials Photosensitive oxide-based nano-materials. New modern applications in the field of photonics (reversible 2D/3D laser microstructuri photovoltaic, etc.) and photocatalysis (depollution, bio-synthesis, etc.) require novel functional inorganic materials with unprecedented high performance and energetic efficiency. These are mainly oxide based nanostructures, often produced by sol-gel and/or RF spray plasma methods. Studies on the elaboration process in close relation with the material electronic structure and related properties are seldom. The goal of NINO-LSPM team is to prepare monodisperse, single phase, highly crystalline and pure photosensitive nanostructured oxides (TiO2, ZnO...) and oxide-based composites fabrication. The process selectivity and kinetics in non-equilibrium condition to control the morphology at the nanoscale will be studied thanks to measurements of the nucleation-growth-aggregation, surface exchange, fluids dynamics, micromixing. With both experimental and theoretical approaches, the coupling between transport phenomena, chemical reactivity and growth of solid structures will be considered. These studies are tightly connected with the studies of the materials electronic and related optical properties, as well as phenomena of light interaction with the materials, in a collaboration with LPL. Metallic based nanostructures. These nanostructures can be produced by self organized single crystal colloids, lithography or PVD growth on surfaces. Using single crystal colloid articles ultra-high enhancement factors are expected. Accurate positioning of the particles must be dramatically improved over substrates obtained by random deposition of the single-crystal particles to guarantee the reproducibility of the desired optical properties. ITODYS and MPQ research teams will work together to combine colloidal assembly techniques with positioning capabilities of electron-beam lithography to design reproducible and efficient plasmonic substrates for biosensing and molecular recognition applications. The influence of the morphology on th plasmonic response will be studied. To act on the metal nanocrystals morphology, PVD-producing core-shell nanodots can be used. Several systems are nowadays under investigation like Cu@Ag, CuO@Ag, Fe@Au, Fe3O4@Au...








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