Modulation of the electronic and magnetic properties of a GaN nanoribbon from dangling bonds

Though GaN nanoribbons (GaNNRs) with H atoms terminating both edges are nonmagnetic semiconductors, the extra dangling bond bands around the Fermi level lead to a transition from semiconducting to metallic, except for the armchair edge GaNNRs (AGaNNRs) with bare N and Ga edges, which are still nonmagnetic semiconductors due to the strong coupling of the dangling bonds of dimeric N and Ga atoms at the same edge. The larger difference in the charge density (ρup-ρdown) for edge bare N atoms and decaying for N sub-lattices away from the edge, as well as the smaller difference in the charge density for edge bare Ga atoms and without decaying for Ga sub-lattices away from the edge is consistent with the magnetic moment of a GaNNR with bare N edge being larger than that of a GaNNR with bare Ga edge. The magnetic moment of a zigzag edge GaNNR (ZGaNNR) with bare N (Ga) edge has nearly half the value of the magnetic moment of a AGaNNR with bare N (Ga) edge. Such a relationship also exists in the number of extra dangling bond states appearing around the Fermi level in the band structures. For ZGaNNRs, the magnetic moment of bare N and Ga edges is larger than either bare N edge or bare Ga edge, but smaller than their sum, implying that there exists an interaction between the dangling bonds at both edges of bare N and Ga edges.