Alpha, beta-unsaturated delta-lactones from copper-catalyzed asymmetric vinylogous Mukaiyama reactions of aldehydes : scope and mechanistic insights.

International audienc

Development of an UV scanning photoluminescence apparatus for SiC characterization

We have adapted a scanning photoluminescence (SPL) apparatus, previously developed for III-V compounds analysis, for the characterization of SiC. The PL mapping is obtained by scanning the sample, fixed to an x-y stage with 1 μm minimal step, under a doubled Ar+ laser beam (244 nm) focused by a microscope objective (×52). For this excitation the spot diameter is about 4 μm. The PL signal can be either directly detected, giving integrated PL intensity, either dispersed using a monochromator, giving spectrally resolved PL (1 nm resolution). The measurements can be realized at room temperature for near band edge studies, or at low temperature (80 K) for deep defects investigation. The gettering effect of non radiative centres by the screw dislocations in 6H-SiC is evidenced using this apparatus

Optical characterization of a strained silicon quantum well on SiGe on insulator

International audienceAn 8  nm thick strained silicon layer embedded in relaxed Si0.8Ge0.2 has been grown on SiGe on insulator substrate in order to reduce the optical response of dislocations present in the SiGe virtual substrate. Photoreflectance measurement shows bandgap shrinkage at Γ point of 0.19  eV which corresponds to a 0.94% strain value close to the one measured in Raman spectroscopy. The luminescence arising only from the strained Si quantum well in high injection conditions reveals clearly two optical transitions observed at 0.959 and 1.016  eV

Application of 3C-SiC quantum dots for living cell imaging

International audienc

Microscopic defects and homogeneity investigations in 4H-SiC epitaxial wafers by UV scanning photoluminescence spectroscopy

UV scanning photoluminescence spectroscopy is applied to 4H-SiC epitaxy characterization. In a first part, the technique is used for triangular defects characterization. The results show that two kinds of defects are present. Some defects are inclusion of cubic SiC which is confirmed by Raman spectroscopy. The other ones consist of staking faults of different thicknesses acting as quantum wells. In a second part, the effective lifetime profile is mapped for a whole 50 mm epitaxy using the variation of room temperature PL intensity versus excitation intensity

Optical investigation of residual doping species in 6H and 4H-SIC layers grown by chemical vapor deposition

We report the results of a series of optical investigations performed on both 6H and 4H epitaxial layers grown at low rate (approximate to 1 mu m h(-1)) in a home-made cold-wall chemical vapor deposition (CVD) reactor. To keep the level of contamination as low as possible, attempts have been made to investigate the origin of residual dopants. In this way, we have found that aluminum comes only from the use of uncoated graphite susceptors. When using a SIC coated susceptor, we have found that the protection is only effective for about ten runs. (C) 1999 Elsevier Science S.A. All rights reserved

Radiosynthesis of 3/5-[18F]-fluoropyridines by TEMPO-mediated radiofluorination of pyridinyl iodonium salts

LDM TEPInternational audienc

TEMPO-Mediated radiofluorination of pyridinyl iodonium salts for the preparation of 3/5-[18F]-fluoropyridines

LDM TEPNational audienc

Barrier height homogeneity for 4.5 kV 4H-SiC Schottky diodes

International audience4.5 kV SiC Schottky diodes have been fabricated using Ni as the Schottky contact. A manufacturing yield of 40% is reached for the bigger area diodes (1.6 x 1.6 mm(2)) and of 70% for the smaller ones (0.4 x 0.4 mm(2)). The measured variations of barrier height and ideality factor with temperature do not agree with the thermionic model. This has been interpreted in terms of barrier height inhomogeneities using the Werner model. We extracted an average barrier height phi(b) = 1 eV and its standard deviation (sigma = 90 mV). These two parameters are almost independent of the diode size. The variation of the barrier height distribution with field has also been investigated and shows a dependence similar to that of Schottky diodes realized from other semiconductor materials

Coupling of quantum emitters in 4H SiC nanopillars

International audienceDevelop a scalable integrated process compatible with standard CMOS technologies, to optimize light collection from quantum emitters in SiC. Applications : Technological building block for Single Photon Source, Platform for optical spin manipulation. Conclusion:1) Development of a scalable fast and costless process to design nanopillars in SiC.2) Evidence of V Si and V Si V C signal enhancement.3) Confirmation of V 1 , V 2 line polarization