Investigation of interface between fullerene molecule and Si (111)-7×7 surface by noncontact scanning nonlinear dielectric microscopy

Fullerene (C₆₀) molecules deposited on Si (111)-7×7 reconstructed (7×7) surface were investigated by noncontact scanning nonlinear dielectric microscopy (NC-SNDM) under ultrahigh vacuum conditions. Both topography and induced electric dipole moment of individual C₆₀ molecules were successfully resolved with molecular-scale resolution. Charge transfer from the Si dangling bonds to the C₆₀ molecule occurs and induces an electric dipole moment at almost all C₆₀ sites. On the application of an alternating voltage, the downward electric dipole moment is nonlinearly modulated due to the electric property at the interface. The NC-SNDM technique can thus detect the electric dipole moment induced at interface between the C₆₀ molecule and the Si adatom in 7×7 surface by the charge transfer from the Si adatom to C₆₀ molecule.