The Effect of Hydrogen and Fluorine Coadsorption on the Piezoelectric Properties of Graphene

Motivated by a search for electromechanical coupling in monolayer materials, we study graphene chemically modified by hydrogen adsorbed on one side and fluorine adsorbed on the other side. Such adsorption under experimental conditions can potentially lead to a variety of configurations of atoms on the surface. We perform an exhaustive evaluation of candidate configurations for two stoichiometries, C2HF and C4HF, and examine their electromechanical properties using density functional theory. While all configurations exhibit an e(31), piezoelectric effect, the lowest energy configuration additionally exhibits an e(11), effect. Therefore, both e(31), and e(11), piezoelectricity can potentially be engineered into nonpiezoelectric monolayer graphene, providing an avenue for monolithic integration of electronic and electromechanical devices in graphene monolayers for resonators, sensors, and nanoelectromechanical systems (NEMS).