A systematic study of various edge modified graphene nanoribbons (GNRs) have been performed using a density functional theory method. Particular attention is placed on the possibility of achieving half-metallicity in the graphene nanostructures. Six chemical functional groups, namely, OH, NH 2, N(CH 3) 2, SO 2, NO 2, and CN, are considered for the edge modification. Density functional theory (DFT) calculations with Perdew-Burke-Ernzerhof (PBE) functional suggest that half-metallicity can be realized in zigzag-edged GNRs (ZGNRs) when one edge of the graphene is fully decorated with the OH group while the other edge is decorated with either NO 2 or SO 2 functional group. Moreover DFT/PBE calculations suggest that the half-metallicity can be realized via modification of one edge with hybrid X groups (X ) SO 2, NO 2, or CN) and hydrogen (H) atoms. Two mechanisms can lead to half-metallicity in ZGNRs, (1) chemical-potential mechanism, that is, to create a difference in chemical potential between the two edges by decorating one edge with electron-donating groups and another with electron-accepting groups, which can lead to spinpolarized states in the electronic band gap, and (2) impurity-state mechanism, that is, to introduce a spinpolarized impurity state at the Fermi level through partial modification of one edge with isolated SO 2 groups. More specifically, for a narrow ZGNR, both DFT/PBE and DFT/hybrid Heyd-Scuseria-Ernzerhof calculations show that the impurity-state mechanism can be realized with hybrid SO 2 and H decorated edge. To our knowledge, the second mechanism has not been reported in the literature. A major advantage of the impuritystate mechanism is its insensitivity to the chemical potential difference between the two edges of a ZGNR. As such, the opposing edge to the SO 2-decorated edge can be decorated by a variety of functional groups (e.g., F, H, or OH) to meet the needs for nanoelectronic applications by design.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films