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Dalle C.F.,Institute Delectronique Of Microelectronique Et Of Nanotechnologies
IEEE Transactions on Electron Devices

The potential of vertical differentiated gallium nitride (GaN) transferred electron devices (TEDs) is compared with that of the base flat doping profile TED for the realization of RF power sources at 1 THz. The TED oscillator modeling is a time-domain continuous wave pure sine model. The semiconductor device model is a 1-D numerical physical macroscopic model based on the energy-momentum approach. Differentiated structures of notch, detached notch, and P+ spike (PS) types have been optimized. By contrast with millimeter-wave differentiated TEDs operating in the dipole domain mode, the terahertz TED RF operating mode remains the accumulation layer/transit time mode. Comparison point out that the differentiated doping profile TEDs slightly improve both the TED RF performance and electronic limitation but above all improve the thermal limitation resulting from the high dc bias conditions due to high threshold electric field in GaN. Thus, the PS TED distinguishes itself as the most promising structure. © 1963-2012 IEEE. Source

Wojkiewicz J.-L.,University of Lille Nord de France | Kamchi N.E.,University of Lille Nord de France | Saravanan C.,University of Lille Nord de France | Redon N.,University of Lille Nord de France | And 2 more authors.
European Journal of Electrical Engineering

Hybrid nanocomposites of polyaniline - polyurethane and carbon cobalt nanoparticles materials were synthesized using the co-dissolution method. First the electronic properties of the polyaniline-polyurethane composites were studied in function of the mass fraction of polyaniline in the blend. The composites showed a very low percolation threshold with a maximum of the conductivity of 104 S.m-1. Then the dielectric and magnetic properties were investigated around the percolation threshold in the microwave band (X and Ku band).The knowledge of these physical properties permit to treat, two applications. The first was the use of the polyaniline-polyurethane as an electronic organic gas sensor. The results show the ability of the material to detect ammonia at very low concentrations. The second application is relative to electromagnetic shielding in the microwave band. The results showed that the manufactured materials are very lightweight and thin with performances in agreement with the standards and compatible with aeronautic applications. © 2012 Lavoisier. Source

Krzeminski C.,Institute Delectronique Of Microelectronique Et Of Nanotechnologies | Lampin E.,Institute Delectronique Of Microelectronique Et Of Nanotechnologies
European Physical Journal B

The modelling of interface migration and the associated diffusion mechanisms at the nanoscale level is a challenging issue. For many technological applications ranging from nanoelectronic devices to solar cells, more knowledge of the mechanisms governing the migration of the silicon amorphous/crystalline interface and dopant diffusion during solid phase epitaxy is needed. In this work, silicon recrystallisation in the framework of solid phase epitaxy and the influence on orientation effects have been investigated at the atomic level using empirical molecular dynamics simulations. The morphology and the migration process of the interface has been observed to be highly dependent on the original inter-facial atomic structure. The [100] interface migration is a quasi-planar ideal process whereas the cases [110] and [111] are much more complex with a more diffuse interface. For [110], the interface migration corresponds to the formation and dissolution of nanofacets whereas for [111] a defective based bilayer reordering is the dominant re-growth process. The study of the interface velocity migration in the ideal case of defect free re-growth reveals no difference between [100] and [110] and a decrease by a mean factor of 1.43 for the case [111]. Finally, the influence of boron atoms in the amorphous part on the interface migration velocity is also investigated in the case of [100] orientation. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

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