Polyaniline (C3N) nanoribbons: Magnetic metal, semiconductor, and half-metal

A two-dimensional polyaniline sheet has been recently synthesized and found that it is a semiconductor with an indirect band gap. Polyaniline nanoribbons decomposed from the two-dimensional polyaniline sheet (C3N sheet) are investigated using a density functional theory. The existence of nitrogen atoms in the edge of the ribbons increases the stability and magnetization of the ribbons and make them different from graphene nanoribbons. Unsaturated nanoribbons are magnetic metals so that the armchair C3N nanoribbons are gap-less spin semiconductors in the antiferromagnetic state and half-metals in the ferromagnetic state. A transition from a metal to semiconductor is observed in the armchair C3N nanoribbons when the edge atoms are passivated by hydrogen. The band gap of the hydrogen saturated armchair C3N nanoribbons can be controlled using an external transverse electric field so that its magnitude is dependent on the direction of the electric field. Being a metal or semiconductor in hydrogen saturated zigzag C3N nanoribbons is strongly dependent on the edge atoms so that just ribbons having nitrogen atoms in both edges are semiconductor. An external electric field cannot induce any spin polarization in the zigzag nanoribbons, which is in contrast with what was observed in zigzag graphene nanoribbons.