Symmetry breaking induced bandgap opening in epitaxial germanene on WSe2

Germanene has attracted much attention because the material was predicted to host Dirac fermions. However, the synthesis of germanene is still in its infancy; moreover, the predicted tiny bandgap induced by the spin-orbit coupling is far from practical applications for nanoelectronic devices. Herein, quasi-freestanding germanene with linear dispersion relation of the band structure is well grown on a WSe2/Au(100) substrate. Band structure calculations reveal that the interaction of germanene with the substrate destroys the sublattice symmetry. The energy-dependent contribution of sigma orbitals responsible for band crossing at the Fermi level around the gamma point induces asymmetric density of states at the Dirac point. Upon annealing in ultra-high vacuum, we observe a bandgap opening in germanene of about similar to 0.17 eV, which is attributed to a sublattice symmetry breaking in germanene and the emergence of a net electric field. This work provides an effective method to tune or tailor the electronic properties of germanene, paving the way to germanene-based field-effect applications. Published under an exclusive license by AIP Publishing.

Automated summary

Researchers have successfully synthesized quasi-freestanding germanene with linear dispersion band structure on a WSe2/Au(100) substrate. They found that the interaction between germanene and the substrate destroys the sublattice symmetry and affects its electronic properties. Upon annealing in ultra-high vacuum, a bandgap opening of about 0.17 eV was observed in germanene, providing an effective method to tune its electronic properties.