Etude théorique de la réactivité de la reconstruction (2X2) de l'AIN(0001)

Abstract : The use of individual molecular systems that can act as components with electronic or logical functions requires perfectly controlled interfaces. More precisely, the support on which these systems are deposited and the metal electrodes that allow to contact an individual molecule, are interfaces that require special care in preparation. The growth of two-dimensional (2d) islands of metals on a monocrystalline insulator allows to generate 2d nano-pads that can be used as electron reservoirs by minimizing surface leakage currents. Thus, it is essential to understand the growth modes of metal/insulating systems which are at present poorly known. This work aims at describing and explaining the growth of different metals on the surface of the polar AlN (0001), which is a large gap nitride compound, by calculations based on density functional theory (DFT). In a first step, a detailed description of the various surfaces of the aluminum nitride is presented. DFT calculations permit to rationalize the reconstructions according to the experimental conditions. The (2 x 2)-Nad reconstruction is discussed, since it was observed by atomic force microscopy. In a second step, the case of the deposit of gold atoms is tackled in connection with experimental results. DFT calculations give an overview of the mechanisms that lead to the stabilization of 2d islands on AlN. The adsorption of gold is accompanied, on the one hand, by a vertical charge transfer from the AlN substrate, which satisfies the electrostatic stability criterion for a polar material and, on the other hand, by horizontal charge transfers related to the local acid-base properties of the (2 x 2)-Nad reconstruction. Finally, calculations made on two other metals, magnesium and silver, are exposed. These results open the way to new strategies using polar substrates to develop metallic monolayers on insulating substrates.
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Benoit Eydoux. Etude théorique de la réactivité de la reconstruction (2X2) de l'AIN(0001). Physique mathématique [math-ph]. Université Paul Sabatier - Toulouse III, 2017. Français. ⟨NNT : 2017TOU30137⟩. ⟨tel-01865463⟩

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