High-Resolution Molecular Imaging with STM and AFM using Functionalized Tips

Using NC-AFM with CO terminated tips, atomic resolution on molecules has been demonstrated and the contrast mechanism was assigned to the Pauli repulsion [2] (see Fig.1c) . On the other hand, by using STM and by decoupling the molecules from the metallic substrate by an ultrathin insulating film, the molecular frontier orbitals, i.e. the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO), were mapped [3] (see Fig1b). Moreover, using a CO terminated tip for orbital imaging with the STM, the images correspond to the gradient of the molecular orbitals due to the p-wave character of the tip states [4] (see Fig. 1d).