Insight into the role of functional groups on the mechanical, piezoelectric and electrical properties of an individual reduced graphene oxide wrinkle

Abstract

This work aims to correlate the structural and physical properties (mechanical, piezoelectric, electrical) of individual graphene oxide (GO) wrinkle using advanced modes of atomic force microscopy (AFM). The high stiffness value of GO wrinkles in phase detection microscopy (PDM) indicates the wrinkle has a high sp2/sp3 carbon ratio and is attributed to the strain induced by the curvature of the wrinkle, which decreases the stability of functional groups. Piezo force microscopy (PFM) measurements demonstrated the strain induced and non-switchable piezoresponse on the wrinkle structure. Functional groups attached plane GO region shows switchable polarization with a piezoresponse of 6 pm/V. The ripple type wrinkles have low strain and high conductance due to their small height and two-dimensional (2D) nature. Above 5 nm height, standing collapsed and folded wrinkles transform into a three-dimensional (3D) structure that facilitates tunneling and anisotropy in electron transport. These findings show that by controlling the functional group concentration, strain, and height of an individual GO wrinkle, one can engineer the wrinkles on the GO structure to meet the needs of practical applications.