Increase of charge-carrier redistribution efficiency in a laterally organized superlattice of coupled quantum dots

We report the observation of enhanced charge-carrier redistribution in laterally organized and coupled InAs/InP quantum dots (QDs). We show that a periodic organization appears in the QD plane for a high in-plane QD density (QDD). This organization enhances the lateral coupling between the dots, which is evidenced by photoluminescence and magnetophotoluminescence experiments. Electronic inter-QD lateral coupling results in an improved charge-carrier distribution at low temperature, as shown by electroluminescence on high QDD QD lasers. We conclude that the inter-QD tunneling occurs via the tunneling of excited states through the wetting layer, and discuss the prospects of using coupled QDs for improving the quantum efficiency and dynamical properties of QD lasers

Volume-Diffusion of 59Fe in Al62Cu25.5Fe 12.5 Icosahedral Quasicrystals

The volume diffusion of 59Fe in Al62Cu25.5Fe12.5 Icosahedral quasicrystals is analyzed using classical diffusion techniques. Over the temperature range from 550°C to 800°C, the volume diffusion coefficients show a classical diffusion behavior and the temperature dependence can be expressed by the following relation : [MATH]. In the absence of data on a crystalline phase with similar composition, diffusion coefficients are compared to those obtained for Fe in aluminium and in aluminides (FeAl and Al13Fe4) : no strong peculiarity linked to the quasicrystalline structure appears

Candidate Landing Sites for the Emirates Lunar Mission (ELM) Rashid-1 Rover

International audienc

Investigation of the Regolith Thickness and Boulder Density at the Four Candidate Landing Sites of the Emirates Lunar Mission Rashid-1 Rover

International audienceThe lunar surface undergoes various space weathering and impact processes, which shape the regolith and expose boulders. Using high-resolution Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera imagery and associated Digital Elevation Models, we investigate regolith thicknesses and boulder densities at the four candidate landing sites of the Emirates Lunar Mission Rashid-1 rover: the floor-fractured crater Atlas and the Sinus Iridum, Oceanus Procellarum and Lacus Somniorum maria.The regolith thickness is estimated using the small crater morphology method, by mapping 3,413 central mound, flat-bottomed, concentric craters (&lt; 350 m in diameter). Boulders were counted manually and compared with LRO Diviner rock abundance and mini-RF Circular Polarisation Ratio global maps.There is no obvious correlation between the site's age, average regolith thickness and boulder density.The "Depth-Age hypothesis" is not confirmed here: Atlas (3.8 Gyr) has the thinnest regolith (median:1.2 m), Procellarum (1.9 Gyr) and Somniorum (3.7 Gyr) have similar thicknesses (1.7 m and 1.8 m respectively), and the regolith in Iridum (3.4 Gyr) is the thickest (2.9 m). The estimated regolith p. 2 thickness is highly variable laterally within the landing ellipses. Boulder fields in the landing areas are well-correlated with higher Diviner rock abundance values, and with locally thicker patches of regolith.The relatively thin regolith in Atlas could be related to its complex geology involving multiple volcanic episodes. Orbital estimates of regolith thickness and boulder distribution remain key for landing safety and trafficability assessments during mission preparations, and bring key insights into the local history of the regolith through crater morphologies.</div

Volume-diffusion of 59Fe in Al62Cu25.5Fe12.5 icosahedral quasicrystals

Communication to : 38th Conference on metallurgy, INSTN 95 : 'des Quasicristaux aux Superalliages', Saclay (France), june 20-22, 1995SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1996 n.9 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Optical characterisation of InAs/InP self-assembled quantum dots for optimisation of lasing properties

International audienc

Nonlinear optical properties of silicon carbide (SiC) nanoparticles by carbothermal reduction

International audienceSiC nanoparticles by carbothermal reduction show promising properties in terms of second harmonic and multiphoton excited luminescence. In particular, we estimate a nonlinear efficiency = 17 pm/V, as obtained by Hyper Rayleigh Scattering. We also present results of cell labelling to demonstrate the potential use of SiC nanoparticles for nonlinear bioimaging by simultaneous detection of second harmonic and luminescence