N-Doped Zigzag Graphene Nanoribbons on Si(001): a First-Principles Calculation

The structural and electronic properties of N-doped zigzag graphene nanoribbons (N-ZGNRs) adsorbed on Si(001) substrates are investigated with first-principles density functional calculations. Compared with the free-standing N-ZGNRs, the energy difference between the substitutional doping at the edge and the inner sites is significantly decreased on the Si substrate. The distribution of the extra charge induced by the N substitutional dopant keeps the Friedel oscillation feature, and is a main effect that influences the C-Si bonding strength. When N is doped in regions with high C-Si bond densities, the strain induced by the dopant also plays an important role in determining the C-Si bonding interactions. Similar to the undoped case, the strong N-ZGNR/Si interaction destroys the antiferromagnetic coupling of the edge states in N-ZGNR, leading to a non-magnetic ground state for the N-ZGNR/Si heterostructures.