STM study of C60F18 high dipole moment molecules on Au(111)

Abstract Scanning tunneling microscopy and spectroscopy studies of C 60 F 18 molecules deposited on Au(111) are reported and compared to C 60 molecules both at liquid helium temperature and room temperature (RT). Whereas adsorption and electronic properties of C 60 F 18 single molecules were studied at low temperature (LT), self-assemblies were investigated at RT. In both cases, the fluorine atoms of the C 60 F 18 molecules are pointed towards the surface. Individual C 60 F 18 molecules on Au(111) have a HOMO–LUMO gap of 2.9 eV. The self-assembled islands exhibit a close-packed hexagonal lattice with amorphous borders. The comparison with C 60 molecules clearly demonstrates the influence of the C 60 F 18 electric dipole moment (EDM) on the electronic properties of single molecules and on the thermodynamics of self-assembled islands. Besides, the apparent height value of a separate molecule increases in a self-assembly environment as a result of a depolarization phenomenon.