No indication of graphene or graphite formation is observed, even at the highest magnification. The elemental composition of the film/substrate interface was investigated by EELS line profiles and stacked EELS spectra in Fig. . The analysis reveals that the first few nanometer r-B4C film grown on the C-face is higher in carbon content compared to the r-B4C film on the Si-face. The stacked EELS spectra show that similar chemical environments and bonding states are present for B-K and C-K edge spectra at the apparent film/substrate interfaces on both substrates. This suggests that the higher carbon content on the C-face interface does not result in the formation of free carbon or graphene/graphite layers which would influence a difference in epitaxial growth conditions of B4C between the two substrate surfaces. EDX depth profiles taken across the film/substrate interface for r-B4C grown on the Si-face Fig. (a) and C-face in Fig. , show the oxygen contributions in the elemental composition. As can be seen, there is an increase in oxygen signal starting from the film nucleation r-B4C film grown on the Cface, while it remains at the base level (same as in the substrate) for the film growing on the Siface. Raman spectroscopy reveals the presence of free carbon on the surface of the epitaxial film, as shown in Fig. . The characteristic D, G, and 2D bands of carbon are observed, at 1352 cm -1 , 1595 cm -1, and 2690 cm -1 respectively, only on the epitaxial r-B4C films grown on the C-face.