Characterization of graphene films grown on CuNi foil substrates

The electronic properties of graphene films depend on the number of atomic layers and the stacking sequence between the layers. One method of growing graphene films that are more than one atomic layer thick is by chemical vapor deposition on metal substrates that have non-negligible carbon solubility. This allows precipitation of carbon from the bulk during the cooling phase of the growth process. In this study, graphene films were grown on foil substrates composed of a CuNi alloy with a nominal bulk composition of 90:10 by weight. To determine the average thickness of the graphene films, angle-resolved X-ray photoelectron spectroscopy was used. For films grown at 1050 °C for 5, 25, and 50 min on the CuNi substrates, thicknesses of 1.06 ± 0.14, 1.19 ± 0.13, and 1.87 ± 0.13 monolayers were measured, respectively. Scanning electron microscopy was used to measure the growth morphology of the graphene films and provided a method of confirming the coverages determined by the analysis of the photoemission data. Ultra-violet Raman spectroscopy measurements were also performed on the graphene films, and it was found that the G-peak intensity increases and the frequency decreases with graphene thickness.