The effects of the dangling bond on the electronic and magnetic properties of AlN nanoribbon

Though AlN nanoribbon (AlNNR) with H atom termination is a nonmagnetic semiconductor, the dangling bonds cause magnetic semimetal for zigzag edged AlNNR (ZAlNNR) with bare N edge, magnetic metal for ZAlNNR with bare Al edge or bare N and Al edges, magnetic semiconductor for armchair edged AlNNR (AAlNNR) with bare N edge or bare Al edge. Due to the strong coupling of the dangling bonds of dimeric N and Al atoms at the same edge, the AAlNNR with bare N and Al edges is still a nonmagnetic semiconductor. The magnetic moment of ZAlNNR with either bare N edge or bare Al edge is nearly half of the magnetic moment of AAlNNR with either bare N edge or bare Al edge due to its half number of the dangling bonds in per unit cell with respect to AAlNNR cases. The larger difference charge density between the majority spin and minority spin for edge bare N atoms and decaying for N sub-lattices away from edge, as well as the smaller difference charge density for edge bare Al atoms and without decaying for Al sub-lattices away from edge indicate the magnetic moment of both ZAlNNR and AAlNNR with bare N edge is larger than that of them with bare Al edge. The dangling bonds induce both ZAlNNR and AAlNNR with bare N edge a completely (100%) spin polarization at the Fermi level, indicating such structures can be utilized to construct efficient spin-polarized transport devices.