The elemental compositions and depth profiles of films prepared by successive e-beam evaporation as well as by the thermal co-deposition of Mg and B components, were investigated via Rutherford back-scattering spectrometry. In the case of films deposited by e-beam evaporation, a study was made of both Mg-B precursors and appropriate MgB2 films grown onto glassy C, Si(100) and J-sapphire substrates annealed in situ. For the films co-deposited by thermal evaporation onto R-sapphire substrates and annealed, only ex situ superconducting MgB2 films were investigated. The TC(0) values of all of the MgB2 films ranged from 21 to 30K. Because of a very fine granular structure of the annealed films, confirmed by scanning electron microscopy, it was not possible to identify any MgB2 phase from X-ray diffraction patterns. On the other hand, the Mg2Si phase was detected by XRD of the film/substrate interface, for superconducting film deposited onto Si(100) substrate. The Rutherford back-scattering measurements were performed using a 3.1MeV 4He+ beam. Under these conditions, the 16O(α,α)16 elastic resonance permitted the detection of O in all of the studied samples; especially in B layers. The depth profiles of precursors prepared by successive e-beam evaporation clearly exhibited a multilayer film structure consisting of B and Mg layers. Strong interdiffusion between the layers could be observed after in situ annealing, but some degree of non-homogeneous component distribution could still be observed. On the other hand, MgB2 films co-deposited by thermal evaporation and annealed ex situ were much more homogeneous, although a higher content of O was present.

RBS Characterization of MgB2 Superconducting Films Annealed ex situ and in situ. J.C.Cheang-Wong, M.Jergel, M.Jergel, C.Falcony: Superconductor Science and Technology, 2003, 16, 879-84