Molecular dynamics simulation on the initial stage of 1 eV carbon deposition on silicon
Résumé
The deposition process of 1 eV carbon on silicon has been investigated by molecular dynamics (MD) simulations up to a fluence of 5.3 x 10(14) atoms cm(-2) which corresponds more or less to monolayer coverage. At such low impact energies, atoms are expected to stay on the sample surface, which is also observed up to a fluence of 2 x 10(14) atoms cm(-2). For higher fluence, carbon atoms start mixing into the silicon substrate. This process seems to get initiated by the increasing strain caused by the carbon atoms deposited on the silicon surface, and which leads to some gradual distortions. The latter are important for the migration of carbon atoms into the silicon lattice. During the whole process the top part of the silicon sample gets amorphized and the coordination of the carbon atoms increases from 1 or 2 to mostly 4-fold coordinated carbon atoms. The process can be considered as the starting point of silicon carbide formation and allows to explain how nm thick films can be formed from 1 eV deposition energies. The low carbon concentration of about 7% in the modified layer is, however, too low to observe a transition towards the latter.