Half-filled energy bands induced negative differential resistance in nitrogen-doped graphene

Nitrogen-doping brings novel properties and promising applications into graphene, but the underlying mechanism is still in debate. To determine the key factor in motivating the negative differential resistance (NDR) behaviour of nitrogen-doped graphene, the electronic structure and transport properties of an 11-dimer wide nitrogen-doped armchair graphene nanoribbon (N-AGNR) were systematically studied by first principles calculations. Both the effect of interaction between N-dopants and the effect of doping-sublattice on the NDR were examined for the first time. Taking into account the two effects, N-AGNR becomes metallic or semiconducting depending on the doping configuration, and its Fermi level varies in a large range. NDR was firmly verified not to be intrinsic for N-AGNRs. However, it is totally determined by whether nitrogen-doping induces half-filled energy bands (HFEBs) because it is HFEBs that cross the Fermi level and determine the transport properties of N-AGNR under low biases. With the bias increasing, the transmission spectrum near the Fermi level showed a flag shape, and therefore, the corresponding transport channel is totally suppressed at a certain bias, resulting in the NDR behaviour with a configuration-dependent peak-to-valley current ratio (PVCR) up to 10(4). Our findings give new insights into the microscopic mechanism of chemical doping induced NDR behaviour and will be useful in building NDR-based nanodevices in the future.