Quantum transport in zigzag graphene nanoribbons in the presence of vacancies.

The effect of vacancies on electronic properties of a zigzag graphene nanoribbon is studied. Vacancies are created by removing carbon atoms on the edge and in the bulk. A tight-binding Huckel model and Green's function methodology are employed to calculate conductance, total density of states, and local density of states (LDOS). The results show interesting behaviors that are notably different from the perfect ribbon, including transmission zeros and modulation in conductance, and changes in the LDOS of neighboring atoms, indicating the formation of localized states. A drop in the highest conductance step by a unit of 2 e2/h is observed for all cases, suggesting the loss of a transmission mode with creation of a vacancy. Interestingly, large increases in LDOS of individual atoms are found at the same energy as transmission zeros or dips in conductance near the Fermi energy. These changes can be shown to be localized near the vacancy, suggesting the formation of localized states that may be causing the conductance dips because of destructive interference between channels. [ABSTRACT FROM AUTHOR]