Surface structure and sputtering in amorphous carbon thin films: a tight-binding study of film deposition

A tight-binding simulation of the atom-by-atom deposition of amorphous carbon (a-C) at 100 eV incident energy is presented. More than 500 atoms were deposited. Chains are observed to form on the surface, some of which are sputtered. The good agreement with the experimental sputter frequency data and observation that all such clusters are linear provides strong support for the existence of these chains and the direct emission model of sputtering. The bulk of the grown film is a-C with a tetrahedral bonding fraction of 20%. Experiments have shown that at this incident energy of 100 eV, tetrahedral a-C is the preferred structural form rather than the a-C produced by this simulation. This discrepancy is attributed to the short range of the interatomic potential.