Edge-adsorption of potassium adatoms on graphene nanoribbon: A first principle study

•Armchair graphene nanoribbon with K edge-adsorption becomes a metal while it is a semiconductor in pristine.•The interaction between the K adatom and armchair graphene nanoribbon is purely ionic.•K edge-adsorption can suppress the magnetic moment at the impurity site and its vicinity in zigzag graphene nanoribbon.•A ferromagnetic state is created when introduce K impurities asymmetry in two sides of zigzag graphene nanoribbon. Using density-functional theory calculations, we studied the electronic properties of graphene nanoribbons (GNRs) with potassium (K) atoms adsorption on the edges of GNRs. Our simulations showed that the electronic structure of the armchair GNR (AGNR) is changed from semiconductor to metal due to the charge transfer from potassium adatoms to the edge carbon atoms. It was observed in AGNR that the K adatom edge-adsorbed system is always nonmagnetic and the interaction between the K adatom and AGNR is purely ionic. In zigzag GNR (ZGNR), we found that K edge-adsorption will suppress the magnetic moment at the impurity site and its vicinity while keeping well the edge structure of ZGNR. We also found that if selectively introduce K impurities asymmetry in two sides of the ZGNR, a ferromagnetic state can be created, while it is antiferromagnetic in pristine. Our results suggest that the electronic properties of GNR can be effectively modulated by K edge-adsorption, and that the alkali-metal edge-adsorbed GNRs can serve as potential materials in nanoelectronics and spintronics.