The structural characterization of amorphous thin films and coatings in their as-deposited state using x-rays at shallow angles of incidence

We demonstrate the method of x-ray diffraction at shallow angles of incidence, using the intrinsically highly collimated x-ray beam generated by a synchrotron source, to study the atomic-scale structure of amorphous thin films and coatings in their as-deposited (i.e., on-substrate) state. As the incident angle is decreased, scattering from the film/coating can be isolated as contributions from the substrate are reduced. Systems studied include chemical vapor deposition (CVD) diamond films deposited onto both silicon and steel substrates, where evidence of an interfacial region between the film and silicon wafer has been observed, but we focus on a range of amorphous films/coatings (mixed TiO2:SiO2 sol-gel spun films, hydrogenated carbon films and ''glassy'' carbon coatings, silicon: germanium semiconducting films and alumina coatings). The data are used both to comment upon the systems studied and to elucidate the potential, and the limitations, of the experimental method.