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ELABORATION ET CARACTERISATION D'OXYDES D'ALUMINIUM ULTRA-MINCES POUR UNE APPLICATION AUX JONCTIONS TUNNELS MAGNETIQUES

Abstract : This thesis reports on the development of an original process, the Atomic Layer Deposition and Oxidation (ALDO) procedure, for growing a perfectly homogeneous artificial oxide film with specific chemical composition. The growth method consisted of three steps: deposition by molecular beam epitaxy (MBE) of one atomic monolayer of a specific metal, followed by exposure of 60 Langmuirs oxygen resulting in chemical oxidation at room temperature, and concluding with annealing in ultrahigh vacuum (UHV) conditions. This three-step process was then repeated to increase the thickness of oxide thicknesses using layer-by-layer growth. Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) were used to control the process.

In this thesis, this process was used to grow aluminum oxide thin films on a silver single crystal substrate, Ag(111), and on hydrogenated silicon, Si(001)-H. AES indicated that the oxide composition was close to AlO, with a spectroscopic signature very different Al2O3. Electron energy loss spectroscopy (EELS) and photoemission spectroscopy (PES) using synchrotron radiation, in good agreement with scanning tunneling spectroscopy (STS) results, were used to estimate a band gap close to 6.5 eV, which did not evolve with oxide thickness up to 3.4 nm. Scanning tunneling microscopy (STM) showed that the oxide layer was very homogenous and wetted the silver substrate perfectly. STM images measured through the oxide layer demonstrated electronic transport through the layer and confirmed that the oxide layer was homogeneous in both depth and chemical composition.

Additional techniques, including atomic force microscopy (AFM), transmission electron microscopy (TEM), AES, and LEED, confirmed the high quality of the aluminum oxide thin films grown by ALDO on Si(100)-H and proved the reproducibility of the method. The roughness did not evolve with the growth of the aluminum oxide on silicon, and TEM images showed an abrupt interface between the silicon and the oxide layer. AES, scanning neutral mass spectroscopy (SNMS), and TEM were used to study the stability of these layers as diffusion barriers. The results suggest that this oxide may be useful in microelectronics applications.
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Submitted on : Tuesday, December 2, 2008 - 3:48:29 PM
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Sébastien Vizzini. ELABORATION ET CARACTERISATION D'OXYDES D'ALUMINIUM ULTRA-MINCES POUR UNE APPLICATION AUX JONCTIONS TUNNELS MAGNETIQUES. Physique [physics]. Université de la Méditerranée - Aix-Marseille II, 2008. Français. ⟨tel-00343700⟩

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