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Contribution à l’étude des propriétés de l’interface métal oxyde GeO/Ru(0001) par STM, XPS/ARPES et SXRD

Abstract : This thesis manuscript is dedicated to the study of silicon (SiO) and germanium (GeO) oxides in their ultra-thin forms. Developed by molecular beam epitaxy on the surface of a ruthenium (0001) crystal, these systems can exist in two stable phases. The first one is a monolayer connected to the substrate by covalent bonds forming a metal-oxide interface. The second one is a weakly interacting bilayer disconnected from the substrate. The weakness of the Van der Waals interactions allows its exfoliation to integrate it into functional heterostructures. In this thesis we study the relationship between structural and electronic properties of these two-dimensional (2D) materials by combining scanning tunneling microscopy (STM), angle-resolved photoemission (XPS, ARPES), surface X-ray diffraction (SXRD) and modelling by DFT methods. Some of our measurements (XPS, ARPES and SXRD) were obtained using synchrotron radiation. If the properties of the silicon oxide (SiO) bilayer are well understood, the description of the electronic properties of the metal-oxide interface proves to be more complex with the impossibility of reconciling the calculations with our ARPES measurements. To understand the origin of this disagreement, we studied the GeO/Ru(0001) interface in the monolayer regime. Our STM and XPS studies validated the atomic model proposed by DFT, including the rotation of Ge-O-Ge bonds and the presence of an interstitial oxygen. Complementary structural studies by SXRD validated the epitaxial relationship proposed by the calculation. Finally, the measured band structure is close to the DFT predictions, contrary to SiO, even if a small disagreement remains. This can be interpreted as an overestimation of the metal oxide bond strength by the calculation introducing a band gap at the Gamma point and at the K point not experimentally visible in ARPES in the case of SiO. Further SXRD measurements on SiO will support this hypothesis.
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Submitted on : Wednesday, November 10, 2021 - 9:08:32 AM
Last modification on : Thursday, November 11, 2021 - 4:00:08 AM


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Thomas Pierron. Contribution à l’étude des propriétés de l’interface métal oxyde GeO/Ru(0001) par STM, XPS/ARPES et SXRD. Physique [physics]. Université de Lorraine, 2021. Français. ⟨NNT : 2021LORR0160⟩. ⟨tel-03423309⟩



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