Study of the impact of chemical etching on Cu surface morphology, graphene growth and transfer on SiO₂/Si substrate

Cleaning copper (Cu) prior graphene deposition, is a crucial step for removing most surface impurities and hence ensuring production of monolayer, large area graphene film with good quality. In this study, we investigated the effect of Cu-cleaning using three different etchants (ammonium persulfate (APS), ferric chloride (FeCl₃) and nitric acid (HNO₃)) for short and long times (30s and 5min) on Cu surface morphology, graphene growth and subsequent transfer onto SiO₂/Si substrate. Our results revealed that 30s-etching gave smoother Cu surface compared to 5min and hence it promoted formation of more uniform graphene film. Furthermore, among the three chemical etchants, APS-30s-etched Cu exhibited the most continuous, uniform, predominantly monolayer graphene film with low density of bi/few-layered domains. This was associated with relatively smoother Cu surface containing significantly lower density of surface particles as compared to other etchants (FeCl₃ and HNO₃). Consequently, 30s-graphene samples yielded better transfer results compared to 5min samples, which exhibited more wrinkles, tears and cracks upon being transferred onto SiO₂/Si substrate. This study highlights the importance of cleaning etchant selection for controlling not only Cu surface morphology but also the characteristics of grown graphene film and its subsequent transfer onto other substrates.