We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO_(1-x)N_x f
ilms with good control over the films nitrogen concentration. In-situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu3+ 4f6 and a corresponding decrease in the number of Eu2+ 4f7, indicating that nitrogen is being incorporated in its 3- oxidation state. While small amounts of Eu3+ in over-oxidized Eu_(1-delta)O thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu3+ in EuO_(1-x)N_x still allows the ferromagnetic phase to exist with an unaffected Tc, thus providing an ideal model system to study the interplay between the magnetic f7 (J=7/2) and the non-magnetic f6 (J=0) states close to the Fermi level.
The epitaxial growth of complex oxide thin films provide three avenues to generate unique properties: the ability to influence the 3-dimensional structure of the film, the presence of a surface, and the generation of an interface. In all three cases,
a clear understanding of the resulting atomic structure is desirable. However, determining the full structure of an epitaxial thin film (lattice parameters, space group, atomic positions, surface reconstructions) on a routine basis is a serious challenge. In this paper we highlight the remarkable information that can be extracted from both the Bragg scattering and inelastic multiple scattering events that occur during Reflection High Energy Electron Diffraction. We review some methods to extract structural information and show how mature techniques used in other fields can be directly applied to the {em in-situ} and real-time diffraction images of a growing film. These collection of techniques give access to both the epitaxially influenced 3 dimensional bulk structure of the film, and any reconstructions that may happen at the surface.
