▎ 摘　　要

Motivated from experimentally realized Cr-chemisorbed graphene, we have systematically explored the electronic properties of organometallic complexes of graphene with covalent monohexahapto-TM (TM = Cr, Fe, Ni) bonds using density-functional theory (DFT) calculations. We show that besides Cr, Fe and Ni can also bind strongly with the graphene. At the experimentally suggested coverage ratio (TM:C = 1:18, TM = Cr, Fe, Ni), our calculations suggest that the computed band gap of perfectly arranged networks of (eta(6)-graphene)-Cr(CO)(3), (eta(6)-graphene)-Fe(CO)(2), and (eta(6)-graphene)-NiCO can be enlarged to 1.08, 0.61, and 0.29 eV, respectively. The inconsistency between the computed gap (1.08 eV) and the experimental gap (similar to 10 meV) for the (eta(6)-graphene)-Cr(CO)(3) is explained, which is possibly due to the existence of regions with relatively lower coverage ratio, in view of the much smaller band gap for (eta(6)-graphene)-Cr(CO)(3) with Cr:C = 1:32 (54 meV) and with Cr:C = 1:50 (20 meV), respectively. Both band gap values are much closer to the measured band gap (similar to 10 meV). Yet, the functionalized graphene shows little structural distortion from its original planar structure. The notable features of the direct band gaps along with the planar structure render the TM-functionalized graphenes quite appealing for applications not only in nanoelectronics but also in optoelectronics such as the infrared detector and solar cell photoanode.