Multiferroic hydrogenated graphene bilayer
We investigated the multiferroic properties of hydrogenated graphene bilayer using first-principles calculations. The proposed material is composed of one fully hydrogenated, and one semi-hydrogenated graphene monolayers. Inside the van der Waals gap, hydrogen atoms are only adsorbed on either top or bottom layer of graphene, thus breaking the centrosymmetry. The calculated electric polarization is 0.137×10−10 C/m, with the transition barrier of switching the polarization to be 393 meV/formula unit. We showed that the ferroelectricity can be preserved down to the atomic thickness. We also studied the domain wall energy and its migration for various domain wall densities, and our results indicate robust polarization configuration against room temperature thermal fluctuation. As graphene is known to be able to sustain large strain, we further explored the ferroelectricity tuning via strain, and found polarization can be effectively tuned up to 20% without perturbing the polarization switching barrier. Our results suggest a realizable multiferroic two-dimensional materials using the most used two-dimensional material graphene.