Effects of substrate material on carbon films grown by laser molecular beam epitaxy

The carbon thin films were grown on different substrates with different buffer layers by laser molecular beam epitaxy (LMBE) with a high purity graphite carbon target. A UV pulsed KrF excimer laser with a wavelength of 248 nm was used as laser source. The structure, surface morphology and other properties of the carbon thin films were characterized by Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and atomic force microscopy (AFM). The results show that the properties of the carbon thin films and the formation of the graphene film have a strong relation to the structure and properties of the substrate. The substrate with a hexagonal wurtzite structure which is similar to the hexagonal honeycomb structure of the carbon atoms arranged in the graphene is more beneficial for the formation of the graphene thin film. In our experiment conditions, the carbon films grown on sapphire substrates with different buffer layers have an ordered structure and a smooth surface, and form high quality tri-layer graphene films.