Enhanced band gap opening in germanene by organic molecule adsorption

We study the geometric and electronic properties of germanene adsorbed with several small organic molecules (SOMs) by using first-principles calculations. The adsorption energies are found in the range from −0.459 to −0.231 eV, higher than those of SOMs adsorbed on graphene and silicene, indicating strong interactions between organic molecules and germanene. These lead to a large enhancement of band gap of germanene with sizable values of 3.9-81.9 meV due to the sublattice symmetry breaking. Noticeably, the characteristics of Dirac cone with low effective mass and high electron mobility are preserved. These findings provide a possible way to design germanene based optoelectronic devices.