Formation and evolution of sp2 clusters in amorphous carbon networks as predicted by molecular dynamics annealing simulations

Abstract

A comparative study of clustering of sp2-bonded atoms in the as-deposited and annealed tetrahedral amorphous carbon (ta-C) films is presented. The as-deposited ta-C with a grown-in compressive stress of ∼10 GPa is modelled using amorphous networks generated by ion-beam film deposition simulations with a modified hydrocarbon potential of Brenner. The ta-C networks were annealed in the temperature range of 600-1200 K, using molecular-dynamics with the same interatomic potential. The size and type of the sp2 clusters were analysed as a function of the annealing temperature as well as the simulation parameters for the stress and temperature control. An essential finding of this study is that at the density less than 3.0 g/cm3 the structure of ta-C can become unstable with respect to formation of large sp 2 clusters. The influence of the sp2 clustering on the film stress is also discussed. © 2004 Elsevier B.V. All rights reserved.