▎ 摘　　要

The structures and electronic states of hydrogenated graphenes with a finite size have been investigated by a density functional theory (DFT) method. Five graphenes of various sizes (n = 2, 4, 7, 14, and 19, where n indicates the number of benzene rings in graphene) were examined as models of a hydrogenated graphene system. The harmonic vibrational frequency corresponding to a C-H stretching mode showed a linear relationship between the frequency and the C-H bond length. The C-H bond formed by the addition of hydrogen atoms was completely polarized as C delta--H delta+ in an equilibrium structure. It was found that the activation barrier is formed by hybridization from sp(2) to sp(3) in the transition region. The mechanism of C-H bond formation on a graphene surface was discussed on the basis of theoretical results. (C) 2010 The Japan Society of Applied Physics