▎ 摘　　要

We present a theoretical study of the effect of defects on the charge-transport properties of gate-all-around graphene nanoribbons field-effect transistors. Electronic transport is treated atomistically using an efficient method we have recently proposed that makes use of a Bloch-wave basis obtained from empirical pseudopotentials and solves the Schrodinger equation with open boundary conditions using the quantum transmitting boundary method. The defects considered here consist in single vacancies at different locations in the ribbon (center and edge of the ribbon; in the source or drain regions or along the channel). We have found that vacancies located at different locations along the ribbon width alter differently the Kekule patterns: Defects at the edge reduce the I-on/I-off more than defects located near the center of the ribbon, and the effect is stronger in narrow ribbons. These results show that any proposed technology based on graphene nanoribbons must be able to control the quality of the material down to a single atom.