C.H. Yang

Edge contact dependent spin transport for n-type doping zigzag-graphene with asymmetric edge hydrogenation

Spin transport features of the n-type doping zigzag graphene nanoribbons (ZGNRs) with an edge contact are investigated by first principle methods, where ZGNRs are C–H2 bonded at one edge while C–H bonded at the other to form an asymmetric edge hydrogenation. The results show that a perfect spin filtering effect (100%) in such ZGNR nanojunctions can be achieved in a very large bias region for the unchanged spin states regardless of bias polarities, and the nanojunction with a contact of two C–H2 bonded edges has larger spin polarized current than that with a contact of two C–H bonded edges. The transmission pathways and the projected density of states (PDOS) demonstrate that the edge of C-H2 bonds play a crucial role for the spin magnetism and spin-dependent transport properties. Moreover, the negative differential resistance (NDR) effect is also observed in the spin-polarized current.

Electronic and spin transport properties in zigzag silicene nanoribbons with edge protrusions

We investigate the electronic transport properties of zigzag-edged silicene nanoribbons (ZSiNRs) with one or two protrusions at the edges using the density functional theory combined with nonequilibrium Greens function method. It is found that the protrusion generally breaks down the edge state along the same edge, which carries current in the junction. For the ZSiNR having an even number of zigzag chains in its width, the protrusions can increase the conductance except for the case of two symmetric protrusions. For ZSiNRs with an odd number of zigzag chains in its width, the introduction of edge protrusions can suppress currents. We also investigate the spin-dependent transport properties of ZSiNR-based devices with antiparallel (AP) magnetism configuration. Interestingly, only non- and symmetric-protrusion models with a width of an even number of zigzag chains show a perfect spin filter effect.

Improving the bias range for spin-filtering by selecting proper electrode materials

Using the non-equilibrium Green’s function method combined with density function theory, we investigate the spin transport for carbon chains connected to electrodes of different materials. When a carbon chain is linked to the C–H (C–H2) bonded edges of H2–ZGNR–H, the carbon chain displays a net spin polarization with a net magnetic moment of 1.367 μB (−0.935 μB) for the C–H (C–H2) bonded edge contacts, but the directions of the net magnetic moment are opposite, and the latter system shows a larger spin conductance. Then, we choose N-doped H2–ZGNR–H as the left electrode, and the right electrode is replaced with a single-capped carbon nanotube, armchair graphene nanoribbon (AGNR), or gold electrode. The conductance and the bias range for perfect spin-filtering of these systems shows obvious differences: the carbon nanotube (Au) system shows weaker conductance, and the AGNR system shows the largest bias range for perfect spin-filtering.