Understanding of ta-C Film Deposition by Means of Atomistic Simulations

Ion beam deposition of carbon films was studied by molecular-dynamics simulations. Using a slightly modified version¹ of the analytical hydrocarbon potential of Brenner, deposition of films with a thickness of up to 10 nm was computed for ion energies E = 10-80 eV, and for substrate temperatures ranging from 100 to 900 K.
The following properties of the calculated films were analysed: (i) sp³ content versus mass density in inner film regions, (ii) binding energies of 3- and 4-fold coordinated carbon atoms in films of different mass densities, (iii) probability distributions for the number of sp³ atoms generated (or annihilated) per deposited ion, and (iv) structure and width of the graphite-like surface regions. As a result, an atomistic picture is provided which shows how the formation of tetrahedral amorphous carbon (ta-C) films is affected by both ion energy and substrate temperature.

¹ H.U. Jäger and K. Albe, J. Appl. Phys. 88, 1129 (2000).