Noncontact atomic force microscope topography dependent on the electrostatic dipole field of individual molecules

Individual acetate (CH₃COO^-) and trifluoroacetate (CF₃COO^-) molecules adsorbed on a TiO₂(110) surface are resolved by noncontact atomic force microscopy. The trifluoroacetate is represented as a short protrusion in the constant frequency-shift topography when compared with the acetate. A permanent dipole moment on the CF₃ group is proposed to compensate for the moment of the COO^- group of the opposite direction and reduce the electrostatic force between the tip and the molecule.