Spin-semiconducting properties in silicene nanoribbons.

We have investigated the relative stabilities and electronic properties of silicene nanoribbons with sawtooth edges (SSiNRs) by first-principles calculations. The SSiNR is more stable than the zigzag silicene nanoribbon (ZSiNR) and has a ferromagnetic ground state with an intrinsic energy gap between majority and minority spin-polarized bands, which shows that SSiNR is a spin-semiconductor. Under an external transverse electric field, the energy gap decreases and even vanishes. Meanwhile, the charge densities of the two edge bands near the Fermi level become spatially separated at different edges. We find also that the electric field-induced features can be achieved by a suitable uniaxial compressive strain. This can be understood from the effect of the Wilson transition. At last, the electronic structures of SSiNRs tuned by electric field and strain together are studied, showing that a small tensile strain makes the SSiNRs more sensitive to the electric field. These results suggest that the electric field or/and strain modulated SSiNRs have potential applications in silicon-based spintronic nanodevices.