First principles calculations of cobalt doped zigzag graphene nanoribbons

We have investigated the stability and electronic properties of Co-doped zigzag graphene nanoribbons (ZGNR) by employing first principles calculations based on density functional theory. The results show that Co impurities settled in antiferromagnetic ground state which is ∼2 meV favourable than ferromagnetic state. The formation energy indicates spontaneous formation of one-edge and centre doped structures, however, one-edge doping is found to be the most energetically favourable configuration. A charge transfer takes place from C to Co atoms which shows the formation of chemical bonding between C and Co. Binding energy also confirms the strong bonding of dopant Co impurity with C. The calculations show that band structures of all the ZGNR is substantially modified due to CoC charge transfer and the characteristic edge states of ZGNR are completely lost. Co-doping induces site independent enhanced metallicity irrespective of the ribbon widths. The broken degeneracy of electronic states in one-edge and centre doped ZGNR is important for spintronic applications.

► All Co doped zigzag graphene nanoribbons (ZGNR) have antiferromagnetic ground state.
► Charge transfer from C to Co depends upon the doping site.
► Edge is the most stable doping site for Co impurities in ZGNR.
► Co doping enhances metallicity in ZGNR irrespective of doping site or ribbon width.