How Diamond-Like Carbon Films Grow

Very dense films of amorphous carbon can have properties—super hardness, chemical inertness, and optical transparency—similar to those of diamond, one of carbon’s crystalline forms. Researchers have learned empirically how to grow films of this so-called diamond-like amorphous carbon (DLC) by depositing carbon atoms onto a carbon substrate. However, they don’t understand theoretically how these films form. Now, combining a machine-learning algorithm with molecular dynamics simulations, Miguel Caro from Aalto University in Finland and colleagues have shown that DLC films form via a “peening” mechanism. In such a mechanism, the impact of a carbon atom on a surface induces pressure waves that locally change the film’s density and, in turn, the orbital hybridization of the atoms in the film.