▎ 摘　　要

Using density functional theory with the effective screening medium method, we studied the electronic properties of graphene nanoribbons with zigzag and armchair edges under a lateral electric field. Our calculations showed that a nearly free electron (NFE) state emerges in the vacuum region outside the leftmost edge of the ribbons and shifts downward with increasing electric field. We also found that electrons are injected into this NFE state of graphene nanoribbons by the critical electric field, which is inversely proportional to the ribbon width. (C) 2014 The Japan Society of Applied Physics