High free carrier density in aluminum adsorbed graphene

Electronic properties of graphene are enriched by aluminum adsorption on surface. The Al adsorbate could be used in n-type transfer doping in graphene. From the first-principle density functional calculations, performed by Vienna ab initio simulation package, there are lots of free conduction electrons in the distorted Dirac-cone structure. Charges transferred from Al to C atoms are about 1.24 e, almost irrespective of the concentration and distribution of the adatoms. A high carrier density is estimated to be $\sim$6$\times$10$^{-14}$/cm$^{2}$ for a ratio of Al/C = 12.5\%. Such carriers mainly originate from the hybridization of Al 3$s$ and C $2p_z$ orbitals, as clearly indicated from the orbital-projected density states, charge distributions and atom-dominated energy bands. Aluminum adsorbed graphene is predicted to have the highest free carriers density except for Al/C $\geq\,$25\% compared with the other adatom-adsorbed systems.