The structure of ultrathin iron oxide films studied by x-ray diffraction

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Title: The structure of ultrathin iron oxide films studied by x-ray diffraction
Authors: Bertram, Florian
Thesis advisor: Prof. Dr. Joachim Wollschläger
Thesis referee: Prof. Dr. Jens Falta
Abstract: In this thesis the influence of deposition conditions and post-deposition annealing on the structure of ultrathin iron oxide films grown on magnesium oxide (MgO) substrates is studied. The main experimental technique used is synchrotron based x-ray diffraction (XRD) but also x-ray photoelectron spectroscopy (XPS) and low energy electron diffractions (LEED) are used to characterize the samples. Studying the dependency of film structure and thickness the stoichiometry and structure is changing with increasing film thickness. For large film thickness bulk like magnetite (Fe3O4) can be observed. With decreasing thickness the oxide phase is shifting towards a wüstite (FeO) phase. When changing the deposition rate and substrate temperature a strong influence on the Fe3O4 film structure is observed. With both decreasing deposition rates and substrate temperatures the occupancy of the tetrahedral sites is strongly decreasing while the octahedral sites remain almost unaffected. By post-deposition annealing under low oxygen atmosphere it is possible to increase the ordering of the tetrahedral sites. However, this is accompanied by significant diffusion of magnesium into the iron oxide film. During post-deposition annealing of a gamma-Fe2O3 film under high vacuum a reduction of the iron oxide is observed. Increasing the temperature, first, a reduction from gamma-Fe2O3 to Fe3O4 is observed. After further increasing the temperature a reduction from Fe3O4 to FeO is observed.
Subject Keywords: iron oxide; thin film; x-ray diffraction; magnetite; Eisenoxid; dünne Schichten; Röntgenbeugung; Magnetit
Issue Date: 3-Jun-2013
Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB06 - E-Dissertationen

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