Selective analysis of molecular states by functionalized scanning tunneling microscope tips

Selective analysis of molecular states in scanning tunneling microscopy (STM) has so far been achieved in a few cases by tuning the bias range of the STM in high resolution measurements. Perylene adsorbed on Ag(110) is imaged mainly through the π-states of the molecule. By functionalizing the STM tip with a perylene molecule a mismatch is created between the energy levels of the STM tip and the molecule adsorbates, so that only the metal states of the underlying silver surface are imaged. This method opens a route for better energy selectivity in electron transport measurements through organic interfaces.