Interplay of surface hydrophilicity and graphene transfer on SiO₂/Si substrate: Implications for electrical conductivity and optical transparency

Graphene, renowned for its exceptional transport properties, stands at the forefront of advanced material science, offering transformative possibilities for next-generation technological applications. Its versatility extends to a myriad of uses, from solar cells and flexible touch screens to gas detection sensors and sophisticated electronic devices. The core of harnessing graphene's full potential lies in perfecting the wet transfer process, a critical step that involves delicately transferring a graphene layer onto a target substrate, such as SiO₂/Si. In this study, we investigate the enhancement of the graphene transfer process by examining the efficacy of three distinct substrate cleaning methods: hydrofluoric acid (HF), piranha solution (PS), and plasma treatment (PT). Our objective is to enhance the wettability of the SiO₂/Si substrate, thereby reducing imperfections in the graphene layer post-transfer. Utilizing advanced characterization techniques such as atomic force microscopy, Raman spectroscopy, and optical microscopy, we comprehensively investigate the surface properties of both the SiO₂/Si substrate and the graphene layer. Our findings reveal significant enhancements in substrate hydrophilicity following treatment with HF and PT. Specifically, we observe a substantial decrease in the water contact angle, decreasing from 85° in untreated samples to 5° and 15° in HF and PT-treated samples, respectively. Conspicuously, all cleaning methods contributed to minimizing defects in the transferred graphene layer. However, PT emerged as the superior method, demonstrating not only enhanced electrical conductivity but also maintaining commendable optical transparency. These findings are not just incremental improvements but a leap forward in the quest for manufacturing high-caliber graphene-based devices.