Morphological characterization of ion-sputtered C-Ag C/C-Ag and Ag/C filmsby GISAXS

A carbon-silver thin film (33 at.% Ag and thickness of 2100 Angstrom) has b een synthesized by co-sputtering of a C-Ag target and characterized by graz ing-incidence small-angle X-ray scattering (GISAXS), a technique that gives a considerably enhanced surface sensitivity. Experiments have been carried out at or near the critical angle of the layer. It is shown that, because C and Ag show no mutual solubility, a demixing occurs during the codepositi on process and silver clusters form within an amorphous carbon matrix. Usin g different incident angles of the X-ray beam, it is demonstrated that two populations of clusters are present in the layer: some large and nearly sph erical on the surface, others smaller and elongated along the direction of the growth of the thin film in the bulk. In the case of a CIC-Ag bilayer, t he surface diffusion is avoided just after the co-deposition process and it is shown that only the small and elongated clusters in the bulk are formed . In the case of a very thin Ag/C layer, there is only surface diffusion an d it is shown that large silver islands are formed on the carbon surface. S uch experiments demonstrate that the growth mechanism that takes place duri ng the co-deposition process involves mainly a surface diffusion of silver and carbon atoms, as opposed to a volume diffusion.