Thermodynamic conditions of ta-C formation at implantation of noble-gas ions in carbon

A new thermodynamic model of formation of tetrahedral amorphous carbon (ta-C) at implantation of C+, Ne+, Ar+, Kr+, and Xe+ ions with energy E from 25 to 1000 eV in carbon target is proposed. Ta-C forms due to momentary co-operative action of increased temperature and all components of pressure in the thermoelastic peak (TEP)—a nanometer-scale region around ion trajectory in target material containing thermalized phonon energy loss and introduced volume of the ion. P,T-trajectories corresponding to the matter state in TEPs of considered species are set on the phase P,T-diagram of carbon. The trajectory location relative to boundary ‘diamond–graphite’ is used for graphic analysis of possibility of ta-C formation by the ion. For the first time, the effectiveness W(E) of «sp2 → sp3» rearrangements in TEP was determined and compared for all considered species. It is shown that function W(E) has one or more maxima differing on value and location for different species. The narrow low-energy maximum appears due to acute maximum of phonon energy loss at the same energy. The broad maximum lying at higher energy is conditioned by energetic dependence of initial radius of TEP. Results of analysis compare with existing experimental data.