Band Structures of Narrow Zigzag Silicon Carbon Nanoribbons

A first-principles investigation on the electronic properties of the silicon carbon nanoribbons (SiC NRs) having zigzag-shaped edges passivated by hydrogen with widths up to 1.7 nm is presented. It is found that, for the zigzag SiC NRs wider than 0.6 nm, the ground state is a ferrimagnetic state that has two different direct band gaps for the spin-up and the spin-down channels near the X point, and thus it is semiconducting instead of half metallic. We also found that the ferromagnetic (FM) state is metallic and has higher energy than the ferrimagnetic state for very narrow zigzag SiC NRs, though the energies of the FM metallic state and the ferrimagnetic semiconducting state are almost equivalent as the width increases. Furthermore, we found that the energies of nonmagnetic semiconducting states that have only one direct band gap were much higher than those of the FM and the ferrimagnetic states. On the other hand, the zigzag SiC NRs narrower than 0.6 nm have only a nonmagnetic semiconducting state that has a large direct band gap of 0.74 eV at the X point. In addition, we found that the Fermi energy of the zigzag SiC NR is susceptible to k-point sampling points in the Brillouin zone integration; when k-point sampling points are not large enough, it can lead to falsity half-metallic ground state. Thus, a properly large k-point sampling should be used in the Brillouin zone integration.