Hydrogen-free amorphous carbon films: Correlation between growth conditions and properties

Hydrogen-free amorphous carbon films with properties ranging between those of graphite and diamond were deposited using a variety of experimental methods. All the different deposition systems apply energetic (E > 10 eV) species to modify the properties of the films (usually called diamond-like carbon (DLC), a name that describes films very different from one another), but they vary in the way in which the energy is transferred to the evolving film and in the amount of control over the deposition parameters. This study reviews our present understanding of DLC growth mechanisms and discusses the correlation between the deposition parameters (e.g. species energy, substrate temperature, substrate material, angle of incidence, deposition rate and environment) and the film properties (density, surface morphology, sp(3)/sp(2) ratio) studied using a host of experimental methods. The data are described in terms of the ''subplantation model'' which regards the deposition process as a shallow implantation. The properties of the films are determined by the amount of carbon species trapped in subsurface positions (internal growth governed by stress) or on the surface (surface growth).