Scanning Tunneling Microscopy Study of Graphene Nanoribbons on Semiconducting Substrates

Recently, several solution-based synthetic techniques have been developed to synthesize Graphene Nanoribbons (GNR), one-dimensional analogs to graphene and close relatives to carbon nanotubes. These large molecules have interesting spectroscopic properties and have been considered as building blocks of nanoelectronic circuits. To this end, it is interesting to isolate single GNRs on surfaces and examine their electronic properties by spectroscopic or transport techniques. A chief barrier to doing this is finding ways to deposit them cleanly on the appropriate substrate so they can be well isolated from their environment. In this work, use a novel dry transfer technique to deposit various GNR molecules on to metallic HOPG and semiconducting WSe₂ substrates. We study their atomic structure with scanning tunneling microscopy (STM) and electronic structure with scanning tunneling spectroscopy (STS). Apart from the spectroscopic properties of the GNRs themselves, we will describe interactions between GNR molecules and the substrate they are placed on, as well as molecule-molecule interactions that can promote chain formation on certain substrates.