▎ 摘　　要

Based on the nonequilibrium Green's function with tight-binding approximation scheme, we study the scanning tunneling microscopy (STM) current from a semi-infinite quantum wire to carbon sites of a zigzag-edge graphene nanoribbon (ZGNR) via an adatom on it. We find that although the existence of local edge states, only the even order number carbon chains near the edge provide good conducting channels, and the STM image should be alternative with dark-bright fringes. This effect has not been shown in previous studies by treating a ZGNR in its entirety, and it may be useful for the STM experimental characterization on graphene samples. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600788]