A nanoscale layer of amorphized silicon is obtained by implantations with silicon ions through a P-doped FZ-silicon wafer material few nanometers below the wafer surface. After a controlled annealing, the amorphized silicon material is sandwiched between two layers of recrystallized silicon. Defects remain at the interface c-Si/a-Si/c-Si. Photoluminescence at very low temperature is experimented to determine the energy levels generated by this design. TEM pictures show that some nanocrystalline elements are located close to the interface surrounded by a-Si. However, the photoluminescence spectra do not present any signal of luminescence from them. This could be due to random sizes of nanocrystals. Then, a scan from energies below the silicon bandgap has been realized at 8 K. The spectrum is composed of multiple narrow peaks close to the conduction band and a broadband from 0.78 eV to 1.05 eV. In order to determine the origin of these signals, spectra of three distinct peaks were collected at different temperatures from 8 K to 120 K. The broadband collapses more rapidly by increasing the temperature than the narrow lines and theirs maxima of intensity differ.
Usually manufacturer's specifications do not deal with the ability of linear sheet polarizers to have a
constant transmittance function over their geometric area. These parameters are fundamental for
developing low cost polarimetric sensors(for instance rotation, torque, displacement) specifically
for hybrid car (thermic + electricity power). It is then necessary to specially characterize
commercial polarizers sheets to find if they are adapted to this kind of applications.
In this paper, we present measuring methods and bench developed for this purpose, and some
preliminary characterization results. We state conclusions for effective applications to hybrid car
gearbox control and monitoring.
Curvature of a multimode optical fiber reduces the numerical aperture and induces radiation losses. We study this phenomenon and we present the "model disadaptation" method to calculate the local numerical aperture and the power attenuation. We exploit the bending effect on the local numerical aperture to propose a new intrinsic optical fiber temperature sensor. The modeling results are experimentally validated for two kinds of optical fibers: a silica-silicone optical fiber and a silica-polymer optical fiber. The simulation and the experimental results are in good accordance and show that the silica-silicone optical fiber sensor can operate between −60 and 152°C with a good response. The silica-polymer optical fiber temperature sensor can sense the temperatures between −249 and 83°C with a good response.
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