Growth of niobium oxide thin films by molecular beam epitaxy

For this thesis niobium oxides (NbO [subscript x]) with the goal of obtaining phase pure epitaxial NbO₂ were grown under variable conditions by molecular beam epitaxy (MBE) on different substrates, mostly (111) oriented strontium titanate. The films were characterized by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) and from that their epitaxial relationship to the substrate was determined. With X-ray photoelectron spectroscopy (XPS) the oxidation states and stoichiometry of the films were determined. Asymmetric NbO₂ Nb 3d core-level spectra are clearly seen for the first time in XPS. Additionally, the film thickness was measured by X-ray reflectivity (XRR). Judging from the XPS spectra and diffraction data the goal to grow epitaxial NbO₂ of high phase-purity was achieved.