Surface and interface morphology and structure of amorphous carbon thin and multilayer films

We review the implementation of X-ray reflection (reflectivity and scattering) techniques for the study of amorphous Carbon (a-C, a-C:H, ta-C) thin and multilayer films and in particular in the determination of the film density and surface and interface morphology, which are intrinsically significant for ultra-thin films. We present studies of various a-C and a-C:H films, which include in particular: i) the morphology of a-C/Si interface, ii) the surface morphology and density evolution during sputter growth of a-C, iii) the morphology of the sp2-rich a-C/sp3-rich a-C interfaces in multilayer a-C films, iv) the universal correlation between the film density and the refractive index of a-C and a-C:H films. We also compare and validate the experimental results with relative results from Monte-Carlo simulations within an empirical potential scheme. The computational results shed light on the atomistic mechanisms determining the structure and morphology of the a-C interfaces between individual sp2- and sp3-rich a-C layers and between a-C and Si substrates.