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. •We perform a study of germanene adsorbed with several small organic molecules (SOMs).•The high adsorption energies indicate strong interactions between SOMs and germanene.•A enhancement of band gap with 3.9–81.9 meV due to the sublattice symmetry breaking.•The small electron effective mass is expected to result in high electron mobility.