Adsorption and manipulation of endohedral and higher fullerenes on $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times 1$

The adsorption of the endohedral fullerene, $\mathrm{La}@{\mathrm{C}}_{82},$ and the higher fullerene, ${\mathrm{C}}_{84},$ on $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times 1$ is investigated using a scanning tunneling microscope (STM) operating in ultrahigh vacuum. Both molecules are found to adsorb directly above the dimer rows that are formed on the $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times 1$ surface, as well as in trough sites midway between dimer rows. Adsorption above dimer rows, not observed for ${\mathrm{C}}_{60},$ is attributed to the larger radius of curvature of these fullerene cages. The response of $\mathrm{La}@{\mathrm{C}}_{82}$ to manipulation by the tip of the STM is also investigated. Molecules in either adsorption site may be manipulated with a threshold gap impedance ∼1.0 GΩ. Owing to a near-commensurability between the molecular diameter of $\mathrm{La}@{\mathrm{C}}_{82}$ and the lattice constant of the Si(100) surface, close-packed arrangements of molecules may be formed.