Atomic-scale study of boron implantation into amorphous carbon

Boron implantation into amorphous carbon substrate has been investigated by molecular-dynamics simulation based on Tersoff empirical potential. The results show that the implanted boron atom is mainly fourfold coordinated. The average size of the implantation-affected region increases linearly with the kinetic energy of the incident boron atom from 150 to 300 eV. Boron implantation leads to a great increase of the total number of the rings in amorphous carbon network and the larger the kinetic energy, the bigger the increasing number. A time-resolved analysis shows that the implantation process can be naturally divided into four stages, among which the second one featuring a decreased coordination number could be analogous to an endothermic reaction, while the third one featuring an increased coordination number could be analogous to an exothermic reaction, which explains why lower substrate temperature and higher thermal conductivity are favorable for achieving higher average coordination number. (c) 2005 American Institute of Physics.