Bonding topologies in diamondlike amorphous-carbon films

The carbon ion energy used during filtered cathodic vacuum arc deposition d etermines the bonding topologies of amorphous-carbon (a-C) films. Regions o f relatively low density occur near the substrate/film and film/surface int erfaces; their thicknesses increase with deposition energy. The ion subplan tation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies < 60 eV and increases for films grown u sing ion energies > 160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical t ransparencies. Bonding topologies evolve with increasing growth energy cons istent with the propagation of subplanted carbon ions inducing a partial tr ansformation of sigma- to pi-bonded carbon atoms. (C) 2000 American Institu te of Physics. [S0003-6951(00)05615-1].