Early stage formation of graphene on the C face of 6H-SiC

Abstract

An investigation of the early stage formation of graphene on the C-face of 6H-silicon carbide (SiC) is presented. We show that the sublimation of few atomic layers of Si out of the SiC substrate is not homogeneous. In good agreement with the results of theoretical calculations it starts from defective sites, mainly dislocations that define nearly circular graphene layers, which have a pyramidal, volcano-like, shape with a center chimney where the original defect was located. At higher temperatures, complete conversion occurs but, again, it is not homogeneous. Within the sample surface, the intensity of the Raman bands, evidences non-homogeneous thickness.

Anisotropic growth of long isolated graphene ribbons on the C face of graphite-capped6H-SiC

“…Recently, it has been suggested that threading dislocations are efficient nucleation centers. 15 Using OM (Optical Microscopy) in the crossed polarization mode and in dark field mode, we evidence mainly two different growth features (see Figure 1a and 1b). the surface where they appear as yellow cones (see Figure 1c).…”

“…We know already that such growth conditions allow the formation of FLG flakes over the whole SiC sample but not homogeneously. 7,15,16 This is because the process is not just intrinsic (simple sublimation of Si and reorganization of the C atoms to form graphene). In most cases, defects facilitate graphitization.…”

“…the surface where they appear as yellow cones (see Figure 1c). 15 Next, surrounding these darker/thicker areas are thinner FLGs which form the grey sea. The mechanism leading to these FLGs was the second one discussed in ref [15], and will be called the "grey sea process" in the following.…”

“…15 Next, surrounding these darker/thicker areas are thinner FLGs which form the grey sea. The mechanism leading to these FLGs was the second one discussed in ref [15], and will be called the "grey sea process" in the following. These FLG form the well known structure shown by AFM in Figure 1d with an average domain size which hardly reaches 1 µm wide.…”

Large-area microfocal spectroscopic ellipsometry mapping of thickness and electronic properties of epitaxial graphene on Si- and C-face of 3C-SiC(111)

“…It is well known that defects in the SiC substrate serve as preferential centers for enhanced Si sublimation. 31 Thus, a higher growth rate of graphene could be expected around these defects, which may explain the formation of such graphite-like islands. The areas with homogeneous graphene layer thickness in Fig.…”