  Graphene, consisting of an inert, thermally stable material with an
atomically flat, dangling bond-free surface is by essence an ideal template
layer for van der Waals heteroepitaxy of two-dimensional materials such as
silicene. However, depending on the synthesis method and growth parameters,
graphene (Gr) substrates could exhibit, on a single sample, various surface
structures, thicknesses, defects, and step heights. These structures noticeably
affect the growth mode of epitaxial layers, e.g. turning the layer-by-layer
growth into the Volmer-Weber growth promoted by defect-assisted nucleation. In
this work, the growth of silicon on chemical vapor deposited epitaxial Gr (1 ML
Gr/1ML Gr buffer) on 6H-SiC(0001) substrate is investigated by a combination of
atomic force microscopy (AFM), scanning tunneling microscopy (STM), x-ray
photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman
spectroscopy measurements. It is shown that the perfect control of full-scale
almost defect-free 1 ML Gr with a single surface structure and the ultra-clean
conditions for molecular beam epitaxy (MBE) deposition of silicon represent key
prerequisites for ensuring the growth of extended silicene sheets on epitaxial
graphene.
