Structure, stability, and stress properties of amorphous and nanostructured carbon films

Structural and mechanical properties of amorphous and nanocomposite carbon are investigated using tight-binding molecular dynamics (TBMD) and Monte Carlo (MC) simulations. In the case of amorphous carbon (a-C), we show that the variation of sp3 fraction as a function of density is linear over the whole range of possible densities and that the bulk moduli follow closely the power-law variation suggested by Thorpe. We also review earlier work pertained to the intrinsic stress state of tetrahedral (ta-C) amorphous carbon. In the case of nanocomposites, we show that the diamond inclusions are stable only in dense amorphous tetrahedral matrices. Their hardness is considerably higher than that of pure amorphous carbon films. Fully relaxed diamond nanocomposites possess zero average intrinsic stress.