Niobium oxide thin films formed by plasma immersion oxygen ion implantation

In analogy to conventional beam-line ion implantation, plasma immersion ion implantation can be combined with a deposition technique to an ion assisted coating process. The structure and composition of a coating and its interface to the substrate can be modified by ion implantation. By means of electron beam evaporation and oxygen plasma immersion ion implantation niobium oxide films were prepared at low substrate temperatures (< 200 degrees C). The film composition and thickness were determined by Rutherford backscattering spectrometry. The results show that oxygen plasma immersion ion implantation leads to incorporation of oxygen into niobium in several steps, corresponding to niobium oxide phases with different stoichiometries. By contrast to conventional beam-line ion implantation at low pressures, two channels for oxidation can be distinguished, ion implantation of high-energy species and radiation enhanced in-diffusion of low-energy species from the plasma. The latter is driven by thermodynamic forces.