First principles calculations of armchair graphene nanoribbons interacting with Cu atoms

We have investigated the electronic properties of bare, H-terminated, Cu-terminated and Cu-doped armchair graphene nanoribbons (AGNRs) using ab-initio approach. We found that H-termination enhances the stability and band gap whereas H extraction introduces dangling bands and lowers the band gap making bare ribbons indirect band gap semiconductors. The calculations revealed that strong hybridization between Cu atoms and AGNRs, lessen the band gap for Cu-terminated ribbons and gives rise to metallicity in Cu-doped AGNRs irrespective of their widths. Formation energy of considered ribbons yield that H-terminated AGNRs with lowest formation energy are most energetically favored, next are one edge Cu-terminated ribbons followed by bare ones whereas both edges Cu-doped ribbons are least energetically plausible. We predict that presence of Cu atoms in GNRs, significantly alter the band gap and can be used in band gap engineering of nanoribbons.

Figure shows the band structure of both edges Cu-terminated AGNR (Na =7). k is the wave-vector parallel to the nanoribbons edge. 0 is the Fermi level.H-extraction introduces dangling bonds at both the edges that reduce the band gap. Cu-terminated nanoribbons are narrow band gap semiconductors whereas Cu-doping make them conducting.Figure optionsDownload as PowerPoint slideHighlights
► Bare armchair graphene nanoribbons (AGNRs) are narrow band gap semiconductors.
► H-termination enhances the stability as well as band gap in narrow AGNR.
► Cu-doped AGNRs are metallic irrespective of their widths.
► Cu-terminated AGNR exhibit oscillatory band gap that depends on their widths.