Reversible Hydrogenation and Bandgap Opening of Graphene and Graphite Surfaces Probed by Scanning Tunneling Spectroscopy

The effects of hydrogenation on the topography and electronic properties of graphene and graphite surfaces are studied by scanning tunneling microscopy and spectroscopy. The surfaces are chemically modified using an Ar/H2 plasma. By analyzing thousands of scanning tunneling spectroscopy measurements it is determined that the hydrogen chemisorption on the surface of graphite/graphene opens on average an energy bandgap of 0.4 eV around the Fermi level. Although the plasma treatment modifies the surface topography in an irreversible way, the change in the electronic properties can be reversed by moderate thermal annealing and the samples can be hydrogenated again to yield a similar, but slightly reduced, semiconducting behavior after the second hydrogenation.