Étude de la structure et des propriétés optiques d’alliages de SiP et de films minces d’oxydes de silicium riches en phosphore

Abstract : This thesis concerns the study of the structural and optical properties of SiP and phosphorus rich silicon oxide thin films. In phosphorus rich Si films annealed at 1100˚C, the formation of SiP crystallites coexisting with Si polycrystals is observed. SiP, which crystallizes in an orthorhombic structure, is a lamellar material which is of potential interest for the development of new 2D materials. The vibrational characterizations are in good agreement with DFT calculations for the SiP alloy. Photoluminescence measurements further suggest that SiP is an indirect bandgap semiconductor with a gap of 1.5 eV. In the case of phosphorus-rich silicon oxide thin films, the structural and optical properties are studied over a wide range of phosphorus concentrations. The photoluminescence intensity of Si nanocrystals follows a complex evolution as the amount of phosphorus increases. For low phosphorus contents, the photoluminescence intensity increases which is interpreted by an increase in the density of nanocrystals and by a passivation effect by phosphorus of the electronic states located at the nanocrystal/matrix interface. Photoluminescence measurements at low temperatures revealed a phosphor-related electronic state located at 0.6 eV below the Si nanocrystal conduction band. This result shows the possibility to incorporate electrically active phosphorus atoms into Si nanocrystals. For phosphorus contents higher than 0.3 at.%, the photoluminescence intensity of Si nanocrystals decreases and then disappears completely. This is related on the one hand to the formation of Si nanocrystals having sizes larger than the exciton Bohr radius in Si (i.e. 5 nm) and on the other hand to the formation of SiP2 nanoparticles crystallizing in an orthorhombic structure. For phosphorus contents above 3 at.%, only SiP2 nanoparticles are observed in the films. The spectroscopies associated with transmission electron microscopy confirm the stoichiometry of the SiP2 compound. The vibrational properties are in excellent agreement with DFT calculations for the SiP2 alloy.
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Sébastien Geiskopf. Étude de la structure et des propriétés optiques d’alliages de SiP et de films minces d’oxydes de silicium riches en phosphore. Physique [physics]. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0024⟩. ⟨tel-02132745⟩

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