Band gap modulation of Janus graphene nanosheets by interlayer hydrogen bonding and the external electric field: a computational study

In this work, density functional theory computations with van der Waals (vdW) corrections revealed the existence of rather strong C-H center dot center dot center dot F-C hydrogen bonding between hydrofluorinated graphene (HGF) monolayers, which have Janus-like geometrics. Interestingly, the individual HGF monolayer is semiconducting with a direct energy gap of 2.82 eV while the HGF bilayer is metallic in its most stable stacking pattern. Especially, applying an external electric field can effectively open a band gap for HGF bilayer, and correspondingly cause a metallic-semiconducting transition. These results open up opportunities in fabricating electronic and optoelectronic devices based on HGF nanosheets, and call for more usage of the weak interactions for band structure engineering.