Substrate effect on doping and degradation of graphene

Graphene is influenced by its surrounding environment, such as adsorbates, charged impurities, and interface traps, owing to its large surface area and ultra-thin thickness. Herein, the effect of substrate conditions on the doping and degradation of graphene is investigated. The hydroxyl (-OH) groups on the silicon dioxide (SiO2) substrate formed by oxygen plasma treatment altered the characteristics of the overlying graphene. On exposure to ultraviolet (UV) light, the p-doping level of graphene on oxygen-plasma-treated SiO2 (P-SiO2) increased and degradation occurred, while graphene on bare SiO2 showed no change. The graphene on P-SiO2 had higher reactivity due to doping induced by -OH groups on the SiO2 surface. The graphene field-effect transistors (G-FETs) on the P-SiO2 also showed the reduced carrier mobility and larger shift of charge neutral point. However, during UV exposure, the device showed sever degradation in electrical conductivity and failure after 60 min. Meanwhile, the device on the bare SiO2 showed negligible changes even after UV exposure. Our results unveil the origin of degradation in the graphene and show a way to prevent the unwanted changes or degradation of graphene, which is highly important for the practical application of graphene. (C) 2021 Elsevier Ltd. All rights reserved.