Possible N-atom positions and formation energies versus N position in a N-doped (a) 13-AR, and (b) 12-ZR. In (b), the two sublattices of graphene are labeled by A and B.
Density of states in N-doped 12-ZRs for varying location of N. (a) DOS in pristine and N-doped 12-ZRs. The Fermi energy has been set to 0. The labels 0, 1, …, 11 correspond to N positions shown in Fig. 1. For each position, the pair of spin-up and spin-down contributions to DOS are shown by positive and negative values. The location of the impurity states in each pair of curves is indicated by an ellipse. (b) Magnetization in 12-ZR with and without N doping. The two edges have opposite spins and are referred to as “up” and “down.” Filled and open circles represent A and B sites, respectively. The N position is counted from the up edge, as shown in Fig. 1.
Energy level dependence on the N position in N-doped 13-ARs, measured from the bottom of the conduction band. The squared wave function of the conduction band minimum in pristine 13-AR is shown in the lower panel. The oscillation of the binding energy is indicated by a dashed line and the 1.5a period of the squared wave function is also pointed out.
Impurity binding energies for N-doped family 1 ARs as functions of width. Filled and open circles are for maximum (N at the edge) and minimum energies. The solid and dashed lines are fitting functions and , respectively.
(Top panels) The electronic band structures of N-doped ARs. (a)–(c) DFT results of edge-doped 11-AR, 12-AR, and 13-AR. The Fermi energy is set to 0, and dashed lines show the N-induced levels. (Bottom panels) Corresponding atomic structures, where carbon is shown in red, hydrogen in green, and nitrogen in blue.
DOS in (a) pristine, (b) zigzag site N-doped, and (c) step site doped (8,1) chiral nanoribbons. The Fermi energy has been set to 0 and the pair of spin-up and spin-down contributions to DOS are shown by positive and negative values. The dashed lines are DOS at edge atoms in (a), and impurity N atoms in (b) and (c).
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