Experimental and theoretical study on the energy-dependent surface evolution and microstructure changes in copper nanostructured composites

Abstract

Many studies have shown that the properties of single carbon system films are governed by the energy of the impinging carbon ions but the role of metal in addition to carbon ions as in diamond-like carbon (DLC) nanocomposites is not yet available. In this study, DLC films doped with different fractions of copper (5 and 15 at%) were fabricated using the pulsed laser deposition technique at varied laser energies, and the energy dependence of surface evolution and changes in microstructures due to the presence of metal were experimentally characterized. By considering the substitution of carbon by copper atoms in the target, the interaction between laser/target and the role of copper ions as envisaged in Saha's equation, the energy of the ions was calculated and good agreement with experimental results was reported. In the presence of copper that increased the ion energy, the excess heat released upon the impingement of ions during the formation of composite films can (1) enhance surface diffusion and promote the formation of nanoislands, and (2) graphitize the diamond bonding in the carbon matrix as seen experimentally. Simulations showed that the metal ions were implanted into the subsurface of the carbon matrix, thus reducing the surface roughness with increasing laser energy as well as increasing copper content. Although the formation of nanoclusters reduced the sp3 bonding of the films, mechanical testing showed that the adhesion strength of the films were improved with the presence of nanoclusters and SiC formed during the deposition.