Hydrogenated graphene oxide (H-G-SiO2) Janus structure: experimental and computational study of strong piezo-electricity response

We have investigated the piezoelectric response of the hydrogenated graphene oxide (H-G-SiO2) stacks both experimentally and theoretically. The piezoresponse force microscopy method and density-functional theory (DFT) calculations were used to study the piezoresponse effect of this structure from both experimental and computational point of views. A monolayer graphene, made by chemical vapour deposition method, is deposited on Si/SiO2 substrate and its surface is then functionalized with hydrogen atoms. The vertical piezoresponse, observed by piezoresponse force microscopy, is measured to be about 2146 pC N-1, that is comparable to the reported state of the art piezoelectric materials such as relaxor-based ferroelectric single crystals. In order to carry out the DFT modelling, a H-Graphene-O Janus structure has been adopted, where graphene is modified by oxygen atoms adsorbed on one side while hydrogen atoms are placed on the other side. Through modelling by DFT calculations, it is revealed that, by applying out-of-plane compressive uniaxial strain, the structure preforms different piezoelectric behaviours, up to three orders of magnitude alteration by the applied strain. The demonstrated approach for enhancing the piezo-response of graphene paves the way for realizing graphene-based nanoscale sensors, actuators and transducers.