High-purity Er3N@C80 films: Morphology, spectroscopic characterization, and thermal stability

Films comprising the endohedral fullerene Er3N@C80 are deposited onto highly oriented pyrolytic graphite (HOPG) substrates in high purity enabled by performing mass-selected low-energy deposition from a cation beam. In the initial stage, the growth on HOPG is dominated by spontaneous nucleation of small 2D islands both on intact terraces as well as the step edges. The island growth exhibits strong differences from films comprising other fullerenes grown by the same method. This behavior can be explained by the surface-diffusion-mediated nucleation model presented in previous work: Dominant components in the behavioural differences are a high intercage dispersion interaction and a lower kinetic energy of cages migrating on the surface in comparison with previously deposited materials. When annealed, the films undergo several competing processes: A small fraction desorbs in the temperature range 700-800 K, another fraction forms covalent intercage bonds instead of the previous purely dispersive bonding mode, and a third fraction probably decomposes to small fragments.