Scanning probe microscopy study of the electronic and piezoelectric properties of multilayer graphene oxide

Abstract

Graphene oxide (GO), a two-dimensional material with tunable changes in electrical, electromechanical, and surface potential behavior, presents great potential for various nanoelectronic and energy-related applications. Herein, we present a detailed nanoscale study of multilayer GO flakes utilizing multimodal scanning probe microscopy (SPM) techniques, which include Conductive atomic force microscopy (C-AFM), Piezoresponsive force microscopy (PFM), and Kelvin probe force microscopy (KPFM). The C-AFM findings of multilayer GO flakes depict charge transport in the vertical direction, with the current profiles remaining relatively stable and showing no significant lateral diffusion. We interpreted this as further evidence of defined percolation pathways combined with sp sup(2)-rich conductive domains, further facilitating charge transport. Current-voltage (I-V) spectroscopic measurements indicate that the conduction mechanisms of GO samples amount to a transition from ohmic conduction to Poole-Frenkel emission, which eventually leads to dielectric breakdown and then current saturation, displaying the structural heterogeneity inherent in GO. PFM data provides an effective out-of-plane piezoelectric coefficient (d sub(33)) of approximately 0.59 pm V sup(-1) and a coercive voltage of 3V. The amplitude data indicate switchable polarization in the butterfly-shaped polarization loop, and a 180 degrees phase reversal confirms the switchable polarization behavior. The KPFM mapping verifies a surface potential of 4.80 eV, consistent with GO being a semiconductor. This work represents the multifaceted role of multilayer GO and establishes its application in nanoelectronics, energy harvesting, and memory devices.