Single and multiple doping effects on electron transport in zigzag silicene nanoribbons

A nonequilibrium Green's function technique combined with density functional theory is used to study the spin-dependent electronic band structure and transport properties of zigzag silicene nanoribbons (ZSiNRs) doped with aluminum (Al) or phosphorus (P) atoms. The presence of a single Al or P atom induces quasibound states in ZSiNRs that can be observed as new dips in the electron conductance. The Al atom acts as an acceptor whereas the P atom acts as a donor when it is placed at the center of the ribbon. This behavior is reversed when the dopant is placed on the edges. Accordingly, an acceptor-donor transition is observed in ZSiNRs upon changing the dopant's position. Similar results are obtained when two silicon atoms are replaced by two impurities (Al or P atoms) but the conductance is generally modified due to the impurity-impurity interaction. When the doping breaks the two-fold rotational symmetry about the central line, the transport becomes spin dependent.