Adsorption and manipulation of endohedral and higher fullerenes on Si(100)-2x1

The adsorption of the endohedral fullerene, La@C-82, and the higher fullerene, C-84, on Si(100)-2x1 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 Si(100)-2x1 surface, as well as in trough sites midway between dimer rows. Adsorption above dimer rows, not observed for C-60, is attributed to the larger radius of curvature of these fullerene cages. The response of La@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 similar to1.0 GOmega. Owing to a near-commensurability between the molecular diameter of La@C-82 and the lattice constant of the Si(100) surface, close-packed arrangements of molecules may be formed.