Assemblée Générale sur la loi de programmation pluriannuelle

Temps d’échange sur les 3 thématiques :

1. Recherche sur projet, financement compétitif et financement des laboratoires
2. Attractivité des emplois et des carrières scientifiques
3. Innovation et recherche partenariale

Observation in-situ dans un microscope électronique à transmission de la croissance par Epitaxie par Jets Moléculaires de nanostructures de semiconducteurs III-V

Gilles Patriarche

Centre de Nanosciences et de Nanotechnologies (C2N), CNRS, Université Paris Sud, Université Paris Saclay, 10 Boulevard Thomas Gobert, 91120 Palaiseau

e-mail : gilles.patriarche@c2n.upsaclay.fr

Le projet Nanomax permet d’observer la croissance de nanostructures jusqu’à l’échelle atomique dans un microscope électronique en transmission. Il est prévu d’étudier en temps réel la croissance de nombreuses nanostructures : nanofils de semiconducteur III-V ou de silicium/germanium mais également des nanotubes de carbone. La croissance est réalisée in-situ dans un microscope électronique en transmission Titan ETEM équipé d’un correcteur d’aberration géométrique sur l’image. Nous avons mis au point pour ce microscope des microcellules à effusion pour éléments III et éléments V permettant de réaliser la croissance in-situ de nanofils de semiconducteur III-V (en particulier GaAs, InAs et GaSb). Les sources sont très collimatées afin d’éviter la contamination de la chambre du microscope, elles émettent sans perturber le fonctionnement du microscope. Nous montrons qu’il est possible d’étudier la croissance par EJM de nanofils de semiconducteur in-situ dans le microscope à une résolution atomique¹.

Les premières études nous ont permis de mettre en évidence l’influence de l’angle de contact du catalyseur sur la phase cristalline des nanofils. L’observation de la croissance à l’échelle atomique en temps réel permet d’accéder directement à la statistique de nucléation des marches et à leur vitesse de déplacement en fonction des conditions de croissance. En modifiant le rapport des flux III/V, on observe en direct le changement de volume du catalyseur et la modification de l’angle de mouillage de la goutte, qui entraîne un changement de la phase cristalline du nanofils (hexagonale vs cubique). Le projet Nanomax est développé dans le cadre de l’Equipex « TEMPOS ».

“Charged graphene as a versatile precursor for multifunctional grafting”

Dr. Noelia Rubio Carrero

Dept. of Chemistry, Imperial College, London

“Intermittent molecular dynamics in disordered porous media:

models versus experiments”

Pierre LEVITZ

PHENIX lab, Sorbonne Université- CNRS, Paris, France

Disordered porous materials and colloidal suspensions are examples of interfacial systems where an internal surface partitions and fills the space in a complex way. Slurry and clay suspensions, soil and muds, fibers, textiles, coating, membranes for nanofiltration (blue energy), cement and concrete, plaster and oil reservoirs are some few examples of these complex interfacial materials. Most of these systems are saturated by a fluid. The level of saturation and the specific properties of this confined fluid strongly influence fluid transport, rheological and poromechanical characteristics of these materials. Various implications in catalyst, nanofiltration, life cycle and durability of various systems can be considered.

The fluid confinement in these restricted geometries involves on the same foot a proximal (or adsorption) layer and a distal region characterized by a bulky confinement in the pore network. The molecular trajectory can be described as an alternate succession of a surface adsorption step followed by an excursion in the confined bulk, generating a new relocation on the surface. As first approximation, the diffusive transport process can be approximated as an intermittent random walk sensitive to the interaction of the vicinal fluid with the interface and to the nature of the bulk confinement.

In the first part of this talk a theoretical analysis of this intermittent random walk dynamics is presented [1]. Two groups of interfacial systems are analyzed: first, suspensions of colloidal particles or macro porous systems exhibiting a relatively weak bulk confinement but variable surface interactions. second, nanometer scale pore networks where excursion of the confined fluid is restricted. When available, Brownian or molecular dynamics simulations are presented. Finally, the possibility to probe this intermittent dynamic using NMR relaxometry is outlined and direct comparison between experimental results and intermittent random walk models discussed [2].

In the second part of this presentation, we propose some possible ways to upscale the fluid dynamics allowing decoupling the scale of the so-called “elementary pore” (which involves adsorption and relocation dynamics) and the long-range exploration, sensitive to the porous network structure. More specifically, in the exploration of a multiscale pore network, we analyze the possibility to quantify the exchange between different length scales using first passage statistics. This approach will be confronted to 2D NMR experiments.

[1]Molecular intermittent dynamics of interfacial water: probing adsorption and bulk confinement, Levitz, P; Bonnaud, PA; Cazade, PA; Pellenq, RJM; Coasne, B. Soft Matter Volume: 9 Issue: 36 Pages: 8654−8663 (2013).

[2] Interfacial and Intermittent Dynamics of Water in Colloidal Systems as Probed by Fast Field-cycling Relaxometry. P. Levitz Field-cycling NMR Relaxometry; New ! Developments in NMR Series, Chap 12, editor R Kimmich, RSC, (2018)

Pour tout contact : ERSEN Ovidiu (0388107028 – ovidiu.ersen@ipcms.unistra.fr)

SEMINAIRE COMMUN IPCMS / CESQ  (Centre Européen de Sciences Quantiques) / EUR QMAT

« A 51-qubit quantum simulator with ultracold Rydberg atoms  »

Sylvain SCHWARTZ

Harvard University (now with laboratoire Kastler Brossel

University of Nagoya

seminaire-Schwartz_23avril2019

« Laser-induced magnetization reversal in Fe/MnAs/GaAs(001) and time-resolved study of MnAs phase transitions »

Franck VIDAL

Institut des Nanosciences de Paris

Affiche – Abstract Seminaire Franck VIDAL

SEMINAIRE DCMI – Labex NIE

« Dynamic Spray-Gun Deposition method for applications  »

Paolo BONDAVALLI

In charge of the transverse topic on nanomaterials,
Thales Research and Technology, Palaiseau, France

Spray gun deposition can be used to fabricate sensors, supercapacitors, flexible memories and conformable Electro-Magnetic Shielding (EMS) layers. Specifically, a mixture of graphene and carbon nanotubes (CNTs) that are acting as a sort of spacers to avoid the restacking of graphene, is used to make new-generation supercapacitors’ electrodes. The latter are characterized by a high conductivity allowing an impressive specific power value of ca. 100kW/Kg. Ionic liquid is also used to increase the energy storage efficacy. Parallel, Graphene Oxide/Carbon Nanofibers-based memories show bipolar behavior and have been cycled 10000 times. They constitute one of the first example of information storage device that can be fabricated using a roll-to-roll implementable method. These devices can open new horizons in the integration of memories for examples in RFID tags or in packages. Finally, embedding several layers of graphene, MWCNTs and carbon nanofibers between polymers X-band frequencies can be absorbed mimicking EMS layers. This is a real breakthrough considering that usually heavy metals are used as ‘trapping’ material, hence, opening the door to new-generations eco-friendly devices.

 » Magnetocaloric Effect : From Energy Efficient Refrigeration to Fundamental Studies
of Phase Transitions  »

Victorino FRANCO

University of Seville, Spain

V-FRANCO_Abstract and Bio