Graphene converted from the photoresist material on polycrystalline nickel substrate

Graphene has attracted attention from both academia and industry owing to its fascinating properties and a wide range of potential applications. Methods for graphene synthesis from solid and liquid carbon sources, including poly(methyl methacrylate) (PMMA), benzene, and other carbon sources, have been reported due to the potential use of a wide variety of carbon feedstocks. In this study, high quality graphene was grown from SU-8-2002 photoresist materials on Ni foil with annealing at 1000°C for 20 min in an ambient mixture of He and H ₂ gas. Scanning electron microscopy image of the as-synthesized graphene on Ni foil indicated that graphene covered the whole area of the Ni foil with various numbers of layers due to the different carbon segregation rate depending on the underlying Ni grain orientation. To unambiguously distinguish the thickness variation of the synthesized graphene layers, they were transferred onto SiO ₂ (300 nm)/Si substrate and were analyzed using optical microscopy, and Raman spectroscopy, which confirmed that the synthesized graphene is composed of various numbers of layers. The thickness dependent G/2D peak intensity ratio (I _G=I _2D) of Raman spectra and their full width at half maximum values obtained from the transferred graphene layers were examined, which were in good accordance with atomic force microscopy analyses.