  Two-dimensional polyaniline sheet has been recently synthesized and found
that it is a semiconductor with indirect band gap. Polyaniline nanoribbons
decomposed from two-dimensional polyaniline sheet (C3N sheet) are investigated
using density functional theory. The existence of nitrogen atoms in the edge of
the ribbons increases stability and magnetization of the ribbons and make them
different from graphene nanoribbons. Unsaturated nanoribbons are magnetic
metals so that armchair C3N nanoribbons are gap-less spin semicon- ductors in
the antiferromagnetic state and half-metals in the ferromagnetic state. A
transition from metal to semiconductor is observed in the armchair C3N
nanoribbons when the edge atoms are passivated by hy- drogen. The band gap of
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 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
