Tuning the hybrid borophene−/graphene-ionic liquid interface: Effect of metal cations on the electronic and photonic properties

Abstract

A density functional theory study of the effect of the adsorption of a mixture of potassium salt and an imidazolium-based ionic liquid on the electronic and optical properties of graphene and borophene is performed. This addition leads to a downward shift of the Dirac cone for both structures due to the electron transferred from potassium to the graphene and borophene sheets. The transferred charge to the wall and the binding energy of potassium are bigger than in the case of the adsorption of potassium on pristine graphene. The Bader analysis shows that the presence of potassium makes the charge distributions in graphene and the layers of boron atoms in borophene more homogenous and the electronic distribution in the sheets is consequently less affected by the electromagnetic interaction with the ions in the mixture. Moreover, the results show that the optical properties are altered by the metallic cation, especially at low frequencies where ionic liquid-enhanced 2D plasmons are registered due to the doping of 2D sheets by electrons transferred from the potassium atoms leading to near zero values of the parallel components of the dielectric function and refractive index.