Structure of reactively sputter deposited tin-nitride thin films:: A combined X-ray photoelectron spectroscopy, in situ X-ray reflectivity and X-ray absorption spectroscopy study

Amorphous tin-nitride thin films were prepared by reactive sputter deposition on smooth float glass substrates in a vacuum chamber with an integrated small magnetron source. The films were investigated using in situ reflection mode X-ray absorption spectroscopy and ex situ Xray photoelectron spectroscopy (XPS). Both the X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) were analysed, yielding bond distances, coordination numbers and Debye-Waller factors. XPS yields the chemical composition and the binding state of the constituents of the films, specular X-ray reflectivity allows the determination of the sample density and of the roughness and its changes with film thickness. The results were compared to those of crystalline Sn3N4, indicating that the electronic and atomic structure of the amorphous films determined by EXATS data analysis are very similar to the stoichiometric reference compound. Two different Sn-N interactions with about 2.09 and 2.19 A bond distance and 4 and 6 nearest neighbours, respectively, are present. These bond distances are slightly relaxed compared to the crystalline reference material, which is consistent with the sample density, which is reduced by about 8% in comparison to Sn3N4. XPS as well as XANES revealed a Sri valence of about 4+ and the presence of nitric bonds, while XPS also suggests that the nitride is slightly decomposed under X-ray irradiation in ultra-high vacuum. (c) 2005 Elsevier B.V All rights reserved.