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.

Automated summary

Graphene has great potential for use in electronic devices due to its unique electrical properties. However, the traditional wet transfer technique leaves microscale impurities from the substrate, degrading the electrical performance of the graphene. To address this issue, a modified transfer process using a temporary UV-treated SiO2 substrate was introduced to adsorb impurities from the graphene before transferring it to the final substrate. The retransferred graphene showed improved electron-hole asymmetry and sheet resistance, indicating that the impurities were eliminated. Overall, this modified transfer process is a promising method for obtaining high-quality graphene for industrial-scale electronic devices.