Tuning electronic band structure of graphene (Gr/SiC) by metal intercalation: Pb and Gd*

Controlled metal intercalation under graphene is a very promising way to build a range of hybrid nanostructures with varying novel electronic and topological phases. Despite its importance, information about the growth conditions (temperature, coverage θ), the intercalation mechanism and intercalation location are missing. Pb is especially important for graphene intercalation because of its high spin orbit (SO) coupling and expected 2-d superconductivity. With high resolution surface diffraction, we have studied Pb intercalation on a mixed surface of single layer graphene and buffer layer on SiC. We found that the onset of intercalation is at the relatively low temperature ~200° C. Domain boundaries between these two phases (single layer and buffer layer graphene) serve as the entry portals for Pb atoms, allowing them to intercalant to the most stable intercalation location: underneath the buffer layer. Gd-intercalated bilayer graphene is also studied to identify different intercalated phases, and how the changes in its band structure are correlated to the Gd intercalation location, which is more challenging to determine in experiment due to more possible locations for the intercalation of bilayer graphene. By globally studying the changing morphology as a function of coverage and temperature, we have identified several Gd-intercalated phases. High resolution scanning tunneling spectroscopy (STS) spatial maps of the topography and differential conductance dI/dV are performed to correlate the Gd-intercalated location to the changes in the local band structure as seen in the spectra.