▎ 摘　　要

The characteristics of field-emission current of a graphene nanoribbon along the direction without finite size effect in the graphene sheet have been theoretically studied. After the work function of graphene nanoribbon is assumed not to change with its width, numerical calculations show that field-emission current density at a given external field decreases with decreasing width of nanoribbon. Such a decrease is especially large when the width of graphene ribbon is a few nanometers. Thus it will lead to an increase in the turn-on electric field. Numerical calculations also show that the effect of the image potential on the field-emission current density decreases with decreased temperature. This implies that to ensure in a workable field-emission device fabricated by graphene nanoribbon, a wider nanoribbon is needed to keep a large field-emission current density. (C) 2011 Elsevier Ltd. All rights reserved.