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Structure and growth of germanene and silicene on Ag and Al surfaces

Abstract : While numerous interesting properties are expected from theoretical calculations for free-standing silicene and germanene, their synthesis remain controversial. This thesis presents an experimental study by scanning tunneling microscopy (STM) and grazing incidence X-ray diffraction (GIXD) of the growth of germanium and silicon on metal surfaces. Three systems have been studied: Ge/Al(111), Ge/Ag(111) and Si/Ag(110). Various ordered reconstructions are observed by STM, depending on the growth temperature. Real-time STM allows me to determine the transitions between these structures. For all cases, STM images acquired during growth show that surface atoms exchange with Si or Ge atoms during deposition. Three ordered structures have been quantitatively analyzed by GIXD. The experimental structure factors obtained have been further compared with the ones simulated from DFT models. For Ge/Al(111), I show that the (3×3) reconstruction corresponds to a two-layer Ge-Al surface alloy, and not to germanene as previously proposed. For Ge/Al(111), I demonstrate the formation of a Ag2Ge surface alloy with a structure similar to the (22×√3) reconstruction of Au(111). However, I demonstrate that further Si deposition on the Si pentamers previously observed on Ag(110) lead to the formation of a dumbbell silicene honeycomb ordered layer.
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Submitted on : Saturday, February 26, 2022 - 8:49:18 AM
Last modification on : Tuesday, March 1, 2022 - 3:30:06 AM
Long-term archiving on: : Friday, May 27, 2022 - 6:07:20 PM


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Kai Zhang. Structure and growth of germanene and silicene on Ag and Al surfaces. Materials Science [cond-mat.mtrl-sci]. Sorbonne université, 2021. English. ⟨tel-03589900⟩



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