A low-energy electron microscopy and x-ray photo-emission electron microscopy study of Li intercalated into graphene on SiC(0001)

Abstract

The effects induced by the deposition of Li on 1 and 0ML graphene grown on SiC(0001) and after subsequent heating were investigated using low-energy electron microscopy (LEEM) and x-ray photo-emission electron microscopy (XPEEM). For 1ML samples, the collected photoelectron angular distribution patterns showed the presence of single π-cones at the six equivalent K-points in the Brillouin zone before Li deposition but the presence of two π-cones (π-bands) after Li deposition and after heating to a few hundred °C. For 0ML samples, no π-band could be detected close to the Fermi level before deposition, but distinct π-cones at the K-points were clearly resolved after Li deposition and after heating. Thus Li intercalation was revealed in both cases, transforming the carbon buffer layer (0 ML) to graphene. On 1ML samples, but not on 0 ML, a ( √3× √3) R30° diffraction pattern was observed immediately after Li deposition. This pattern vanished upon heating and then wrinkles/cracks appeared on the surface. Intercalation of Li was thus found to deteriorate the quality of the graphene layer, especially for 1ML samples. These wrinkles/cracks did not disappear even after heating at temperatures ≥500 °C, when no Li atoms remained on the substrate. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.