C70 self-assembly on In- and Tl-adsorbed Si(111)3×3-Au surfaces

Abstract Behavior of C 70 fullerenes adsorbed onto the In- and Tl-modified Si(111) 3 × 3 -Au surfaces at room temperature (RT) and 112 K has been studied using scanning tunneling microscopy observations and compared with the known results for the C 60 s on the same surfaces. During island growth at 112 K, both C 70 and C 60 are characterized by the same critical island size i =1. The difference is in an island shape as C 70 s tend to form chain-like islands built of double or triple molecular rows along the [ 1 ¯ 10 ] Si(111) substrate directions. At RT, C 70 s have a lower mobility as compared to C 60 s. In contrast to the C 60 magic islands, the C 70 islands do not demonstrate any strong preference for specific shapes or sizes. Extended C 70 arrays exhibit a stripe-like 3×1 reconstruction where a single row of bright fullerenes mediated by a double row of dim fullerenes. The reconstruction is due to the different orientations of C 70 s within the layer which does not relate to the structure of the underlying Au/Si(111) substrate. This is in contrast to the hexagonal reconstructions of C 60 s where the bright fullerenes occupy the specific adsorption site atop Au trimers. The difference in the behavior of C 70 and C 60 is plausibly affected by the non-spherical shape of C 70 molecule and a greater intermolecular C 70 -C 70 interaction.