Electronic Characterization of 9A-GNR on H:Si(100) using a Scanning Tunneling Microscope

We present the electronic characterization of a new solution-synthesized type graphene nanoribbon (GNR). The GNR was synthesized with two different precursors to form coves along the length of an N=9 armchair GNR. The GNR also contains two different functional end groups, -NO2 and -NH2, with each synthesized to attach to the two different precursors. Atomically precise graphene nanoribbons with functional end groups have the potential for further modification and integration into complex electronic structures. We use the dry-contact transfer (DCT) method to exfoliate the GNRs onto hydrogen passivated Si(100) in a room temperature ultra-high vacuum (UHV) scanning tunneling microscope (STM). The bandgap and density of states are probed using scanning tunneling spectroscopy (STS) and current imaging tunneling spectroscopy (CITS). We find that GNRs tend to cluster in groups and form weak bonds at the functionalized ends. We also find evidence of missing phenyl groups during synthesis which form extra-large coves in the final structure of the GNR. Simulation data indicates that the DFT bandgap is 1.4 eV and an increased density of states over the NO2 end group. Experimentally we see that one end of the GNR appears to be metallic using STS, which we attribute to the NO2 end group. The bandgap appears to have a lateral dependence from 1.7 eV to 2.3 eV along the GNR which will be explored in more detail. Finally, we present the effects of using nanolithography to depassivate the H:Si(100) below the GNR.