Stress Reduction Behavior in Metal-incorporated Amorphous Carbon Films; First-Principle Approach

The stress reduction behavior in metal-incorporated amorphous carbon films was investigated by the first-principle calculation. We calculated the total energy of the system with changes in bond angles between the incorporated metal (Ti,Mo, Cr, W, Ag, Au, Al, Si, etc) and the carbon atoms by using DMOL³ computational software package. The four carbon atoms are arranged as a tetrahedron, with a carbon or metal atom at the center. The total energy increased substantially as the bond angle deviated from the equilibrium value when a carbon atom is located at the tetrahedron center. However, with a replacement by a metal atom at the center of the tetrahedron, the increase in the total energy due to the distortion in bond angle was significantly reduced. The pivotal action of the metal atoms dissolved in the carbon matrix would be more significant when noble metals having filled d-shells are incorporated compared to the transition metals having unfilled d-shells. These atoms have a weak and more isotropic bond with carbon atoms as confirmed by the electron density distribution.