Memory effect in the deposition of ${\mathrm{C}}_{20}$ fullerenes on a diamond surface

In this paper, the deposition of ${\mathrm{C}}_{20}$ fullerenes on a diamond $\mathrm{}\left(001\right)\mathrm{}-(2\mathrm{}\times 1)$ surface and the fabrication of ${\mathrm{C}}_{20}$ thin film at 100 K were investigated by a molecular dynamics (MD) simulation using the many-body Brenner bond order potential. First, we found that the collision dynamic of a single ${\mathrm{C}}_{20}$ fullerene on a diamond surface was strongly dependent on its impact energy. Within the energy range 10–45 eV, the ${\mathrm{C}}_{20}$ fullerene chemisorbed on the surface retained its free cage structure. This is consistent with the experimental observation, where it was called the memory effect in $“{\mathrm{C}}_{20}$-type” films [P. Melion et al., Int. J. Mod. B 9, 339 (1995); P. Milani et al., Cluster Beam Synthesis of Nanostructured Materials (Springer, Berlin, 1999)]. Next, more than one hundred ${\mathrm{C}}_{20}$ (10–25 eV) were deposited one after the other onto the surface. The initial growth stage of ${\mathrm{C}}_{20}$ thin film was observed to be in the three-dimensional island mode. The randomly deposited ${\mathrm{C}}_{20}$ fullerenes stacked on diamond surface and acted as building blocks forming a polymerlike structure. The assembled film was also highly porous due to cluster-cluster interaction. The bond angle distribution and the neighbor-atom-number distribution of the film presented a well-defined local order, which is of ${\mathrm{sp}}^3$ hybridization character, the same as that of a free ${\mathrm{C}}_{20}$ cage. These simulation results are again in good agreement with the experimental observation. Finally, the deposited ${\mathrm{C}}_{20}$ film showed high stability even when the temperature was raised up to 1500 K.