Researchers Kyle Ritter and Joseph Lyding at the University of Illinois in Urbana-Champaign have utilized an ultrahigh vacuum scanning tunneling microscope (STM) to study the size-dependent semiconducting behavior in nanometer-scale graphene. Using an in situ stamping technique called dry contact transfer developed in their research group, they applied single and bilayer graphene specimens to a hydrogen passivated silicon (100) surface. STM spectroscopy was then used to provide an atomistic view of the graphene electronic structure. For graphene monolayers with lateral dimensions of 2–10 nm, the observed energy gaps ranged from 0.1 to 1 eV and scaled inversely with the lateral dimensions. Furthermore, atomic level detail of the silicon substrate could be “seen” through monolayer graphene, but was screened out for the case of graphene bilayers. These results have been reported in Nanotechnology.
Future work includes coupling detailed spatially resolved spectroscopic measurements with atomistic simulations to provide valuable insight into the variation of the graphene electronic structure with its atomic structure. The ultimate goal is to “bandgap engineer” the electronic structure of the graphene through the use of STM nanolithographic techniques.
