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Theses

PROPRIETES DE TRANSPORT DE MICROSTRUCTURES ET NANOSTRUCTURES DE SILICIUM.

Abstract : This thesis work deals with the study of transport properties, of both charge and spin, in silicon-based microstructures and nanostructures.
We have studied the fabrication process of connected low section (100 x 8 nm2) silicon nanowires (SiNWs) using atomic force microscope (AFM) lithography on thinned silicon on insulator (SOI) samples. Electrical measurements highlighted typical Field Effect Transistor (FET) behaviour of these SiNWs. Electron trapping in oxide or at interfaces is responsible of the cumulative depletion of the wires during the successive I(V) measurements. Electron release is obtained by application of a voltage on the wire gate. So the wires exhibited a memory effect in which the writing / reading process occurs by electron trapping / de-trapping controlled by application of a positive / negative voltage on the device gate.
Furthermore, we studied the spin transport in a silicon substrate. Numerical evaluation of spin transport in drift-diffusive regime reveals spin diffusion and spin precession lengths of several microns, under a weak external magnetic field. Such dimensions are compatible with present technology of ICs. Electrical measurements carried out on a magnetic memory integrated on silicon (MEMIS), specially designed for this study, showed electron injection and collection efficiency. However, no magnetoresistance was detected probably due to the low quality of interfaces in the hybrid heterojunctions ferromagnetic metal/insulator/silicon (FMIS). Thus, we proposed to test extra FMIS structures such as Co/AlO(~1 nm)/Si and Co/MgO(~1 nm) /Si, fabricated with less thermal treatments. The direct tunnelling transport in oxide was obtained in these junctions, which would allow spin injection coherence in prospective spin devices.
Finally, we have characterized rectifying junctions Ferromagnetic semiconductor/semiconductor (MSS) such as Ge3Mn5/Ge which seem to be particularly suitable for spin injection.
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Submitted on : Thursday, November 29, 2007 - 3:23:38 PM
Last modification on : Tuesday, October 20, 2020 - 3:10:28 AM
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Nabil Rochdi. PROPRIETES DE TRANSPORT DE MICROSTRUCTURES ET NANOSTRUCTURES DE SILICIUM.. Matière Condensée [cond-mat]. Université de la Méditerranée - Aix-Marseille II, 2007. Français. ⟨tel-00192856⟩

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