Tuning flexoelectricity and electronic properties of graphene nanoribbons*

Flexoelectricity — the coupling between polarization and strain gradients is an electro-mechanical phenomenon, which is observed by bending a material. Flexoelectricity is present in a variety of materials including soft matter, liquid crystals, and crystalline materials, but is only significant at small length-scales, where high strain-gradients develop. Here, the flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first-principles calculations. We predict that the inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. Our results are an important advance towards the understanding of flexoelectric and electronic properties of low dimensional materials, which will be useful for potential flexible electronic applications.