Epitaxial functional oxide integration on germanium

Germanium, with its higher hole and electron mobility is a potential candidate to replace silicon as a channel material in a field effect transistor in the future. The integration of high quality crystalline oxides on semiconductors still remains a challenge due to lattice defects, a lattice constant mismatch as well as a possible thermodynamic instability between the thin film and the substrate. In this work we report the integration of functional oxides on germanium, which exhibit a wide variety of useful physical properties such as ferromagnetism, superconductivity or ferroelectricity which are of high interest for future electronic devices as i.e. for the development of a ferroelectric field-effect transistor. The focus of this thesis lies on the study of the high-[kappa] and ferroelectric material barium titanate, grown on germanium (001) by using an oxide molecular beam epitaxy machine. Further characterization techniques as x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, atomic force microscopy and electrical measurements are used to study the properties of the oxide films and to obtain a deeper understanding of their interface qualities with the substrate. This research contributes significantly for the development of a ferroelectric field-effect transistor and oxide heterostructures on germanium in general.