Le Si Dang CNRS researcher and member of the “Nanophysique et Semiconducteurs” group of the Néel Institute, is the 2010 laureate of the Gentner-Kastler prize for his contributions to the study of polaritons in low-dimensional semiconductors and for the discovery of their Bose-Einstein condensation.
60 years ago and half a century after helium gas was first liquefied by Kamerlingh Onnes in Leiden (1908), the CNRS laboratory in Grenoble became a centre for helium liquefaction. Today the liquefaction centre at the Néel Institute is the largest in France. We recall here the history of this development from its origin to the present day.
Does the classical Stefan-Boltzmann law for blackbody radiation apply to nanometre-size objects ? To answer this question, the heat flux in vacuum between two surfaces at different temperature and separated by distances between one micron and 100 nm has been measured accurately and compared to theory. The research involved two CNRS laboratories, the Néel Institute and the Charles Fabry Laboratory of the Institut d’Optique (Paris). At the nanometre scale, the measurements show large discrepancies with the Stefan-Boltzmann law.
Josephson junction chains are attracting a lot of interest currently due to their possible applications in the fields of metrology and quantum information. For example, under microwave irradiation of frequency f, such chains should exhibit exact current quantization I=2nef, where 2e is the charge of a Cooper pair and n is an integer number. Therefore, these chains could be used for the definition of a new quantum current standard. In view of the many possible applications, we have measured the ground state of a Josephson junction chain. We have analysed our results in terms of “quantum phase-slips”, the central phenomenon occurring in such superconducting networks.
Nanowires are considered to be very promising as building blocks for nano-scale devices and as a new route to access the physics of low dimensional systems. For III-N compounds (nitrides of Group III elements), nanowire heterostructures provide a new way to create quantum dots, with greater flexibility as compared to the classic transki-Krastanow growth mode because the dot height and the material composition can be better controlled. Furthermore, while the strain induced by the large lattice mismatch usually leads to high dislocation density in planar III-N nanostructures, it can relax elastically (radially) in thin nanowires, allowing dislocation free growth.
The 6th ESONN (European School On Nanosciences and Nanotechnologies) took place from August 22nd to September 12th 2009 in Grenoble. ESONN is a summer school organised each year by the Université Joseph Fourier and Grenoble INP, with the essential participation of the CNRS and the CEA. It is designed for doctoral students and young researchers interested in nanosiences. ESONN’s specificity is to associate lectures given by top European specialists with practical sessions at the “Centre Inter-universitaire de Micro-Electronique ” (CIME) and in Grenoble research Institutes.
There have been long-standing research and teaching collaborations between Romania and France, most notably with Grenoble. Néel Institute plays an active role through its hosting of colleagues and students from several Romanian universities, in particular Cluj-Napoca (Babes-Bolyai). The latter’s Faculty of Physics has many common interests with Néel Institute (Condensed Matter Physics, Magnetism, Materials...), which has led to a constant influx of Master level Romanian students to Grenoble. Many students have continued to PhD level at the Université Joseph Fourier or Grenoble INP, in many cases the thesis work being co-supervised.
In the present economic and ecological context, two primordial fields of research in Earth Sciences are (i) developing methods for sequestration of CO2 in mineral form as stable carbonate rocks and (ii) understanding the formation of metal-ore deposits in view of the prospection of new, mineable resources. A common aspect of these two research fields is understanding the complex processes of dissolution/precipitation of rocks in aqueous fluids.
Micro flux sources produce magnetic fields which are spatially modulated at the micron scale. They have many potential applications in the field of magnetic MEMS (Micro-Electro-Mechanical-Systems), as well as for biasing, diamagnetic levitation, the manipulation and trapping of particles and atoms, etc. The magnetic force on a magnetic particle submitted to the field of such a flux source depends on the field and on the field gradient created by the source. Since the field gradient is inversely proportional to the size of the field source, the force per unit volume increases as its size is reduced.
Diamond is a wide bandgap semiconductor (Eg = 5.5 eV) with astounding electronic, thermal, optical, mechanical and chemical properties, which have been recognized for several decades. Steady progress has been achieved in understanding and mastering crystalline quality and defects, dopant concentrations, carrier mobility and saturation velocity, breakdown voltage and surface terminations, which control the electrical properties of homoepitaxial layers used in electronic devices.
Last October, a new generation of detectors for millimetre-wave astrophysics was tested at the IRAM observatory on Pico Veleta near Granada (Spain). The KIDs (Kinetic Inductance Detectors) development is the result of a strong collaboration between a number of European groups, coordinated in Grenoble by the Néel Institute’s HELFA group. The collaboration includes SRON-Holland (in particular A. Baryshev), University of Cardiff, Max-Planck Institute for Radioastronomy, Bonn and Università La Sapienza Roma.
Patterned in vitro neural networks can form functional logical circuits allowing a first approach to the computational complexity of the brain. We grow neural networks where the inter-cellular information flow is accurately controlled by exploiting substrates with specifically designed micro-patterns. The networks are positioned on silicon nanowires patterned into field effect transistors dedicated to the study of the neurons’ electrical activity.
The Néel Institute has a well established expertise in crystal growth. Among the many growth techniques used, crystal growth in solution (flux method) at high or low temperatures (close to room temperature) allows synthesis of crystals that undergo a phase transition or decomposition before melting. The major drawback of these techniques, when compared with growths from the melt, is the limited growth rates that can be achieved. As a result, growth runs can extend over several months for very large crystals, hence the interest in developing techniques able to increase growth rates by an order of magnitude. The expertise of the Néel Institute “Matériaux, Optique Nonlinéaire et Plasmonique” team in such techniques is the basis of a joint study involving the CNRS, the CEA and the company St Gobain Crystals in view of the growth of giant crystals for the “Laser Mégajoule” facility.
Recent progress in the field of molecular electronics now allows for directly integrating molecular objects into electrical on-chip circuits.
A new generation of temperature regulators for cryogenics applications has been designed at the Néel Institute. This new system, iMARCT, is built to a modular autonomous, design around an Ethernet interface, and can regulate temperatures between 10 mK and 300 K. Forty instruments have already been constructed and transfer of the technology to an industrial partner is under way.
For the past fifteen years, the processes developed on the Néel Institute’s Nanofab platform were variants of “top-down” technologies. Exploration of the physical properties of nano-objects, often randomly arranged, has led to the development of new “bottom-up” procedures evolving from the work of several Néel Institute research groups.
Florence Marchi (Néel Institute researcher and Associate Professor at Université Joseph Fourier) has received the prize for innovative education at the 8th French-speaking Colloquium for Teaching Systems and Information Technologies and Sciences (CETSIS). The prize was awarded for her presentation of the force-feedback nanomanipulator, which allows students and the general public to “touch the Nanoworld with their fingertips”.
Despite decades of theoretical and experimental efforts, the condensation and evaporation of fluids inside porous media are still not fully understood. The ANR (National Research Agency) project ”HEVEPOR”, a collaboration led by Néel Institute and involving the LPTMC (University Pierre and Marie Curie, Paris) and the GES (Montpellier University UM2), aims to unravel the mechanisms responsible for the observed hysteresis between evaporation and condensation, and to understand their relationship to the porous media microstructure. A specific goal is to assert the influence of disorder and confinement on the liquid-gas transition. With that goal, we study a novel experimental system, helium in transparent porous glasses. Using helium as a fluid allows a direct observation of the physical phenomena at play.