Effect of applied electrical potential and humidity on friction of Graphene-Based thin films

Abstract

Understanding the nanofrictional characteristics of thin films in various conditions is important for fabricating nanoelectronic devices and micro-/nanoelectromechanical systems with high functionality and reliability. This study investigated the nanofrictional characteristics of composite thin films of graphene oxide (GO) and cellulose nanocrystals (CNCs) and of reduced graphene oxide (rGO) and CNCs, namely GO/CNC and rGO/CNC thin films, under an applied electrical potential and humidity by using a conductive atomic force microscope (AFM). For all films, the coefficient of friction (CoF) was affected by the applied electrical potential and enhanced mechanical properties resulting from strong interactions of GO and rGO with CNCs. Furthermore, the friction force increased with the electrical potential at low humidities (relative humidity (RH) < 40 %) because of the electrostatic force effect, while for RH>40 %, the friction force sensitively increased with the electrical potential because of the puckering effect. At high humidities (RH>40 %) and high electrical potentials (>4 V), the friction force decreased as the electrical potential increased, owing to the electron leakage phenomenon. This study also characterized the altered nanofrictional behavior influenced by interfacial phenomena in the films under an electrical potential and humidity, and it provides design guidelines for fabricating nanoelectronic devices and micro/nanoelectromechanical systems.