C60 adsorption onto the one-atomic-layer In films on Si(111) surface

We have studied C60 adsorption onto the In-induced Si(111) reconstructions, Si(111)2 × 2-In, Si(111)-hex-√7 × √3-In, and Si(111)-rec-√7 × √3-In, which all represent essentially one-atomic-layer In films residing atop a bulk-like Si(111) substrate. The reconstructions have various In densities, incorporating 0.75, 1.0, and 1.2 ML of In, respectively. We have found that C60 adsorption onto these reconstruction is accompanied by the mass transport within In atomic layer, which is manifested by developing the domains of a more dense In/Si(111) reconstruction on the surface in between C60. This observation provides a direct evidence for the displacement of In atoms from beneath C60 to the surrounding surface area. The plausible driven force of the C60-induced In displacement is a tendency of C60 to change relatively modest bonding with In layer to a more stronger bond with Si(111) substrate.