Electronic and magnetic properties of 3d transition-metal atom adsorbed graphene and graphene nanoribbons

Graphene is an example of a truly two dimensional crystal  with interesting properties. Carbon based materials are expected to be building block of tomorrow's  technology. Carbon nanotubes can be metallic or semiconducting, depending on their chirality. This could lead to a fully carbon-based elecronics. However, the lack of control on the chirality prevents carbon nanotubes from electronic application. Recent studies indicate that graphene nanoribbons can be produced in a highly controlable manner unlike CNTs. Graphene nanoribbons appear to be superior to nanotubes. Functionalization of graphene by adatoms can also provide several different applications. Chemical functionalization and substitutional doping have been investigated for many years in nanotubes with  the aim of tailoring their properties for sensing, transport, and chemical and optical applications. It is thus natural to do a similar investigation for graphene. In this study, we studied electronic and magnetic properties of graphene and graphene ribbons functionalized by 3d-transition metal (TM) atoms.  The binding energies, electronic and magnetic properties of TM atoms adsorbed to a single side and double sides of graphene are investigated according to a well-defined pattern of absorbtion.  We find that 3d-TM atoms can be adsorbed on graphene with binding energies ranging between 0.10 to 1.95 eV depending on their species and coverage density. Upon TM-atom adsorption graphene becomes magnetic metal.  Graphene nanoribbons with armchair edge shapes also adsorb TM-atoms.  Binding to the edge hexagons yield the minimum energy state for all TM-atom species examined in this work, and all ribbon widths under consideration.  Energy band structures of 3d-TM atom adsorbed graphene nanoribbons display different magnetic properties. Fe and Ti adsorbed ribbons become half-metallic whereas depending on the ribbon width and the adsorption atom species, AGNRs also become FM or AFM metals, magnetic semiconductors.

H. Sevinçli, M. Topsakal,  E.Durgun  and S. Ciraci
PHYSICAL REVIEW B 77, 195434 (2008)
Editorially selected  for Virtual Journal of Nanoscale Science and Technology.