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Etude par STM des états d’hybridation pd induits par un atome de Cr inséré dans la surface de GaAs(110)

Abstract : In this thesis, we investigate by scanning tunneling microscopy (STM) the effects of surface and coordination on the electronic properties of a transition metal atom occupying a cationic site in the GaAs(110) surface.By an in situ deposition method, we deposited Cr adatoms on cleaved GaAs(110) surfaces with coverage rates lower than a monolayer. And by applying voltage pulses close to a few target magnetic adatoms using the STM tip, we have manipulated them and substituted them with Ga atoms in the two first layers of the GaAs(110) surface. Thus obtaining magnetic atoms having different atomic environments, i.e. Cr adatoms, Cr atoms forming three bonds with three neighboring As atoms (Cr in the first layer) and Cr atoms forming four bonds with four neighboring As atoms (Cr in the second layer).To study the electronic properties of these transition atoms as a function of their position in the GaAs surface (110), we have realized on them STM imagery with different voltage bias as well as scanning tunneling spectroscopy (STS). They showed topographic forms with different mirror symmetries and revealed different numbers of STS peaks in the gap of the GaAs surface (110) according to their atomic site.By collaboration, density of states (DOS) calculations and simulations of STM images were carried out on Cr atoms occupying cationic sites in the GaAs bulk and in the five first layers of the GaAs surface (110) using the density functional theory (DFT). Agreements between the theoretical calculations and our experimental results have allowed us to show (i) that the measured STS peaks on the Cr atoms correspond to peaks of DOS resulting from an hybridization between the d states of Cr and the p states of their neighbors atoms of As and Ga ; (ii) that our STS measurements on the Cr atoms in the two first layers are affected by the symmetry breaking at the GaAs(110) surface; (iii) that a splitting of some induced states in the GaAs gap (110) occurs when a Cr atom passes from the first to the second surface layer; (iv) and that the measured topographic STM images on Cr atoms inserted in the first two layers of the surface correspond to wave functions of specific pd hybridization states
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Khalifa Badiane. Etude par STM des états d’hybridation pd induits par un atome de Cr inséré dans la surface de GaAs(110). Physique [physics]. Université Sorbonne Paris Cité, 2017. Français. ⟨NNT : 2017USPCC189⟩. ⟨tel-02095227⟩

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