Self-organized formation of layered carbon–copper nanocomposite films by ion deposition

The quasi-simultaneous deposition of low energy-mass-selected C+ and metal+ ions leads to the formation of metal–carbon nanocomposites. In the case of C+ and Cu+ deposition, a homogeneous distribution of small copper clusters in an amorphous carbon matrix is expected. However, at a certain C+/Cu+ fluence ratio and energy range, alternately metal-rich and metal-deficient layers in an amorphous carbon matrix with periods in the nm range develop have been observed. The metal-rich layers consist of densely distributed crystalline Cu particles while the metal-deficient layers are amorphous and contain only few and small Cu clusters. The formation of multilayers can be described by an interplay of sputtering, surface segregation, ion induced diffusion, and the stability of small clusters against ion bombardment. This formation has been investigated for the a-C:Cu system with respect to the ion energy and the C+/Cu+ fluence ratio. The sputter coefficient SM = rf SCCu + SCuCu is the parameter to switch between layer growth (SM < 1) and homogeneous cluster distribution (SM > 1).