Spatial variability in large area single and few-layer CVD graphene

Variability in graphene can result from the material synthesis or post-processing steps as well as the surrounding environment. This is a critical issue for the performance of large area devices as well as for the large-scale production of micro- and nano-scale graphene devices, leading to low yield and reliability. The aim of this study is to investigate variability of single and few-layer graphene structures, on different substrates, and the effects it has on its electronic properties. We demonstrate a combination of Kelvin probe force microscopy (KPFM) and non-contact Fourier transform infrared spectroscopy (FTIR) measurements for centimeter-scale quantitative mapping of the electrical variability of large-area chemical vapor deposited graphene films. KPFM provides statistical insight into the influence of micro-scale defects on the surface potential, while FTIR gives the spatially averaged chemical potential of the graphene structures. Test structures consisting of single-, bi- and few-layer graphene on SiO₂ and Al₂O₃ were fabricated and analyzed.