ABSTRACT
The free electron densities arising from the n-type dopings are very high and quite close to those observed in alkali-adsorbed graphenes. The metal atoms, the alkali ones excepted, might provide the multiple outermost orbitals for the multi-orbital hybridizations with the out-of-plane p bondings on the honeycomb lattice. This will dominate the fundamental properties of Al-, Ti- and Bi-adsorbed graphene nanoribbons, in which they are explored thoroughly by using the first-principles calculations. The free conduction electrons provided by per Al adatom in a unit cell are worthy of closer examinations. Energy bands strongly depend on the edge structures; there are certain important differences in zigzag and armchair graphene nanoribbons. The Al-adsorbed zigzag graphene nanoribbons exhibit the diverse magnetic configurations, being different from and similar to the spin arrangements of the alkali-adsorbed ones. The carrier density and the variation of carrier density can provide very useful informations the orbital bondings, energy bands, and charge transfer.
