Controlled hydrogenation of graphene sheets and nanoribbons.

The electronic properties of graphene sheets and nanoribbons with different degrees of hydrogenation have been investigated using a combination of charge transport and Raman spectroscopy experiments. The field-effect transistor mobility of graphene is shown to be highly sensitive to the treatment time during atomic hydrogen dose and follows an exponential decrease with time. Raman spectroscopy demonstrates linearly increasing defect-band intensity, and when considered together with transport data, the relationship between graphene mobility and the crystalline size of intact sp(2) carbon regions can be derived. Further, the increase in width of the voltage plateau for monolayer and bilayer graphene points to the formation of midgap states. For partially hydrogenated graphene, the temperature-dependent transport in these states shows a weak insulating behavior. A comparison of Raman spectrum and conductivity data of partially hydrogenated monolayer and bilayer graphene suggests that the latter is also quite susceptible to adsorption of hydrogen atoms, despite a stiffer lattice structure.