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.