Nanostructural characterization of amorphous diamondlike carbon films

Nanostructural characterization of amorphous diamondlike carl,on (a-C) film s grown on silicon using pulsed-laser deposition (PLD) is correlated to bot h growth energetics and film thickness. Raman spectroscopy and x-ray reflec tivity probe both the topological nature of three and four-fold coordinated carbon atom bonding and the topographical clustering of their distribution s within a given film. In general, increasing the energetics of PLD growth results in films becoming more "diamondlike," i.e., increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is differe nt for material near the substrate interface compared to material within th e bulk portion of an a-C film. A simple model balancing the energy of resid ual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding cluste rs in a growing a-C film.