Nanoscale array of inversely biased molecular rectifiers

We report a scanning tunneling microscopy (STM) and spectroscopy (STS) study of an electron donor (hexa-peri-hexabenzocoronene, HBC) covalently linked to six electron acceptors (anthraquinone, AQ) in self-assembled monolayers at the graphite–liquid-interface. The HBCs and AQs order in two-component nanoscale arrays with distinctly different electronic properties of their elements as reflected by the relative STM contrast depending on the sample bias. STS reveals an inverse rectifying behavior of the two moieties within the tunneling junction, which is attributed to resonantly enhanced tunneling through the HOMO of the HBC and the LUMO of the AQ.