Tuggle, J. Eremeev, G.V. Kelley, M.J. Reece, C.E. Xu, H. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-TUPB046 English 669-672 TUPB046 ion niobium electron SRF cavity Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-TUPB046 http://srf2015.vrws.de/papers/tupb046.pdf The structure and composition of Nb3Sn films obtained by diffusion coating niobium coupons and SRF cavities were investigated by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS) and electron back-scatter diffraction (EBSD), including native surfaces, depth profiles and cross-sections. We find that the native surface oxide is significantly tin-rich, we have measured depth profiles. We find that the grains apparent in the SEM images are individual crystallites having no evident relationship to the substrate or each other.