The first MRSEC Seminar of the Fall 2012 Series welcomes Dr. Dan Dougherty, a faculty member of the School of Physics at North Carolina State University in Raleigh,NC, on September 18, 2012 at 3:00pm in the Marcus Nanotechnology Building conference rooms located on the first floor.  His talk is title: Doping Effects Due to the Intercalation of Epitaxial Graphene on SiC: Local Spectroscopy of Image-Potential States

Abstract:

An exciting route to controlling the electronic properties of graphene on SiC(0001) is to “intercalate” new atomic species beneath the 6√3 buffer layer, decoupling it from the substrate to form a new graphene sheet with properties partially-determined by the intercalant atoms.  This approach is an attempted adaptation of the fascinating property variation that can be found in graphite intercalation compounds [1]. So far, intercalation of graphene on SiC(0001) has been carried out for numerous systems, including Ca to enhance electron doping effects [2] and H to create quasi-neutral graphene [3].

           Since intercalation processes in these systems only involve the top-most surface layers, they are likely to be more kinetically efficient than bulk intercalation processes in graphite.  I’ll illustrate this in the case of Na, which is not known to intercalate graphite [1], but which readily intercalates single layer graphene on SiC at room temperature [4].  Scanning Tunneling Microscopy shows several different Na-intercalation structures that can coexist for epitaxial graphene.  Local tunneling spectroscopy of image-potential-derived surface state allows a probe of electron doping effects in this system and also comparison with electronic structure calculations.  Finally, I'll describe similar STM/STS experiments for hydrogen intercalation in this system and discuss implications for the origin of interlayer states in graphite [5].