Electronic Structures of Germanene on MoS2: Effect of Substrate and Molecular Adsorption

Abstract

Germanene, a two-dimensional (2D) Dirac semimetal beyond graphene, has been recently synthesized on a nonmetallic substrate, which offers great opportunities for realization of germanene-based electronic devices. Understanding the effects of substrate and chemical modification on the electronic properties of germanene is thus crucial for tailoring this novel 2D material for future applications. Herein we investigate the structure, interlayer interaction, and electronic band structure of monolayer germanene supported on various transition metal dichalcogenide (TMD) substrates. A band gap of 38–57 meV can be opened by the TMD substrates due to breaking of lattice symmetry of the germanene sheet. An electron donor molecule, tetrathiafulvalene (TTF), is exploited to noncovalently functionalize the germanene on MoS2 substrate. The electron transfer from TTF to germanene disturbs the Dirac cone of germanene and leads to an augment of the band gap up to 180 meV. Meanwhile, the charge carriers of the hybrid syste...