Selective analysis of molecular states by functionalized scanning tunneling microscopy 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. Correspondingly, perylene adsorbed in a close-packed monolayer on Ag(110) is imaged mainly through the pi states of the molecule. By contrast, functionalizing the STM tip with a perylene molecule leads to a mismatch between the energy levels of the STM tip and the molecule adsorbates and, instead, images only the metal states of the underlying silver surface. The observation opens a route for better energy selectivity in electron transport measurements through organic interfaces.