B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
Received October 9, 2019, published online December 27, 2019
The total electron state densities are calculated and analyzed for graphene nanoribbon boundaries of various chirality, as well as the local density of states for individual atoms, pertained to such nanoribbons. The presence of sharp resonances near Fermi level in total densities of electron states is demonstrated for the graphene nanostrips with zig-zag boundaries. Noticeably, these resonances emerge only at local densities of atoms pertained to the sublattice directly outward the nearest boundary, i.e., with dangling bonds on the constituent atoms. The semiconducting gaps appear in the spectra of graphene nanobands, which contain the boundaries of armchair chirality with a number of constituent atomic lines either multiple of three or yielding residual one when divided by three. Gap-width depends on the band width only and is the same for all the atoms in the band. Electron spectra of nanostrips with the boundaries of armchair chirality evidence a metallic behavior, if the residual of the number of atomic lines, divided by three, is equal two, though semiconducting gaps on local densities are still manifested for a number of the atoms.
Key words: graphene nanoribbons (nanostrips), electron spectrum, dimensional quantization, local density of states.