  We report on the growth of epitaxial ZnO thin films and ZnO based
heterostructures on sapphire substrates by laser molecular beam epitaxy (MBE).
We first discuss some recent developments in laser-MBE such as flexible
ultra-violet laser beam optics, infrared laser heating systems or the use of
atomic oxygen and nitrogen sources, and describe the technical realization of
our advanced laser-MBE system. Then we describe the optimization of the
deposition parameters for ZnO films such as laser fluence and substrate
temperature and the use of buffer layers. The detailed structural
characterization by x-ray analysis and transmission electron microscopy shows
that epitaxial ZnO thin films with high structural quality can be achieved, as
demonstrated by a small out-of-plane and in-plane mosaic spread as well as the
absence of rotational domains. We also demonstrate the heteroepitaxial growth
of ZnO based multilayers as a prerequisite for spin transport experiments and
the realization of spintronic devices. As an example, we show that
TiN/Co/ZnO/Ni/Au multilayer stacks can be grown on (0001)-oriented sapphire
with good structural quality of all layers and well defined in-plane epitaxial
relations.
