(color online) Structures of SiNRs with (a) zigzag and (b) armchair edges. Here the number of the longitudinal diatomic chains of the SiNRs N = 6 in panel (a) and N = 9 in panel (b). The rectangle denotes a unit cell including 2N atoms. a=3.86 Å is the lattice constant of the zigzag SiNRs and b = 3 a = 6.69 Å is that of the armchair SiNRs. A perpendicular electric field E and an in-plane magnetic field B are applied.