New method to synthesize graphene by using C60 as carbon source

Abstract

The synthesis of large area high-quality graphene has been one of the main interests of the scientific community after the discovery of this exceptional material. Many different experimental protocols have been followed with the aim of achieving a controlled, scalable and low-cost production of this carbon allotrope [1]. To date, most of the works have been focussed on growing graphene from hydrocarbon gaseous or liquid precursors. In this work, we describe a new protocol to grow high-quality graphene by physical vapour deposition (PVD) using C60 molecules evaporated in ultra high vacuum conditions (UHV) on Cu foils substrates. The use of low carbon solubility Cu substrates is really appealing for graphene growth due to its inexpensiveness and the possibility of post-growth graphene transfer on arbitrary substrates [2]. The quality of the resulting graphene layer has been assessed by the combination of complementary surface characterization techniques After growth, in-situ LEED images exhibit a polycrystalline graphene pattern. Ex-situ AFM and Raman spectroscopy (Figure) were used to determine the quality of the graphene layer. XPS experiments showed the C1s XPS core level signature of high quality graphene layers. ARPES measurements unveil the linear behaviour of electrons near Dirac point and show a clear n-doping of 0.7 eV consequence of the interaction between graphene and substrate. Finally, DFT calculations allow to understand the mechanisms that determine this interaction. This work reveals that the use of C60 as precursor molecules is an alternative route for growing high-quality large area graphene layers on Cu foil substrates [3]. The advantages of this PVD method lie in the use of a lower synthesis temperature as compared to that of conventional CVD methods, a low amount of oxygen-containing species in the surface due to the clean UHV environment and the formation of single graphene layer due to the singularity of being a self-limiting process.