Modulating the electronic structures of graphene by controllable hydrogenation

The evolution of electronic structures of hydrogenated graphene with different amount of hydrogen (H) coverage was investigated by ultraviolet photoemission spectroscopy and optical absorption spectroscopy. Raman spectroscopy and x-ray photoelectron spectroscopy were used to monitor and evaluate the H coverage. At low H coverage, the sp(3) C-H bonds embedded within a sp(2) C matrix behave as defects in graphene and depress the delocalized pi electron system. At high H coverage, two localized pi electron states originating from the sp(2) C clusters encircled by the sp(3) C-H matrix appear in the electronic band structures, and an opening of a band gap has been observed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3524217]