Investigation of the structural properties of thin amorphous carbon films and bilayer structures

Thin amorphous carbon films and bilayer structures with different carbon layers were investigated by means of both ex-situ and in-situ X-ray reflectivity, X-ray photoelectron spectroscopy and optical absorption spectroscopy. The films were grown either by magnetron sputtering of a graphite target or, starting from the gas phase, by ion-beam deposition and by plasma assisted chemical vapour deposition. The X-ray reflectivity measurements revealed the existence of a transitional layer between the substrate and the film, and of an ultrathin transitional layer at the interface between two carbon layers. The structural parameters of both the films and these interfaces were investigated. It was found that films obtained by magnetron sputtering and by deposition from the gas phase, in spite of having different optical and electrical properties, have practically the same electron density. Such multilayer structures of constant electron density open the way to the formation of what could be defined ‘latent superlattices’.