Self-assembly of C60 fullerenes on quasi-one-dimensional Si(111)4 × 1-In surface

Using scanning tunneling microscopy observations, self-assembly of C60 fullerenes in the course of room-temperature adsorption onto Si(111)4 × 1-In reconstruction and after subsequent annealing at temperatures ranging from 150 to 450 °C has been studied. Adsorbed C60 fullerenes have been found to occupy off-centered positions on In-atom rows forming linear chains with a maximal length of eight C60 molecules. Intermolecular spacing within the regular chains equals three lattice constants of Si(111) surface. Two energetically different adsorption states of C60 have been detected, one of which is occupied preferentially at room temperature, while occupation of the second (more tight) state dominates at temperature above ~ 150 °C. In the first state, C60 fullerene resides plausibly in a continuous rotation, while in the second state a C60 molecule is fixed tightly in a single orientation with a C60 hexagon pointing upward. Transition of C60 fullerenes to the more stable state is accompanied by expelling In atoms from the Si(111)4 × 1-In reconstruction.