▎ 摘　　要

We have performed a systematic study to investigate how transition metal (TM) atoms affect the electronic properties of zigzag graphene nanoribbons (ZGNR). We considered the interaction of ZGNR and TM taking Ni as a terminating element as well as a substitutional dopant at single vacancy sites. Present calculations revealed that all the considered ribbons have ferromagnetic ground state. The calculated binding energy varies from -6.86 eV to -10.55 eV for Ni-termination and -4.07 eV to -10.35 eV for Ni-doping that shows a rather strong binding. The present calculations revealed that edge doped ribbons are energetically more favourable than the center doping. Ni-termination enhances the metallicity with a little distortion in the characteristics band structure of ZGNR whereas in Ni-doping, the characteristics band structure is lost and a dispersive band appears at Fermi level. The position of this dispersive band is independent of the ribbon width and thus equalizing the metallicity in ZGNR. Width independent metallicity is crucial at nano regime.