Charge Transport in UV-Oxidized Graphene and Its Dependence on the Extent of Oxidation

Graphene oxides with different degrees of oxidation are prepared by controlling UV irradiation on graphene, and the charge transport and the evolution of the transport gap are investigated according to the extent of oxidation. With increasing oxygenous defect density [Formula: see text] , a transition from ballistic to diffusive conduction occurs at [Formula: see text] cm [Formula: see text] and the transport gap grows in proportion to [Formula: see text]. Considering the potential fluctuation related to the [Formula: see text] puddle, the bandgap of graphene oxide is deduced to be [Formula: see text] meV. The temperature dependence of conductivity showed metal–insulator transitions at [Formula: see text] cm [Formula: see text] , consistent with Ioffe–Regel criterion. For graphene oxides at [Formula: see text] cm [Formula: see text] , analysis indicated charge transport occurred via 2D variable range hopping conduction between localized [Formula: see text] domain. Our work elucidates the transport mechanism at different extents of oxidation and supports the possibility of adjusting the bandgap with oxygen content

A Modified Wet Transfer Method for Eliminating Interfacial Impurities in Graphene

Graphene has immense potential as a material for electronic devices owing to its unique electrical properties. However, large-area graphene produced by chemical vapor deposition (CVD) must be transferred from the as-grown copper substrate to an arbitrary substrate for device fabrication. The conventional wet transfer technique, which uses FeCl3 as a Cu etchant, leaves microscale impurities from the substrate, and the etchant adheres to graphene, thereby degrading its electrical performance. To address this limitation, this study introduces a modified transfer process that utilizes a temporary UV-treated SiO2 substrate to adsorb impurities from graphene before transferring it onto the final substrate. Optical microscopy and Raman mapping confirmed the adhesion of impurities to the temporary substrate, leading to a clean graphene/substrate interface. The retransferred graphene shows a reduction in electron–hole asymmetry and sheet resistance compared to conventionally transferred graphene, as confirmed by the transmission line model (TLM) and Hall effect measurements (HEMs). These results indicate that only the substrate effects remain in action in the retransferred graphene, and most of the effects of the impurities are eliminated. Overall, the modified transfer process is a promising method for obtaining high-quality graphene suitable for industrial-scale utilization in electronic devices