Comparison of graphene formation on C-face and Si-face SiC {0001} surfaces

Abstract

The morphology of graphene formed on the ( 1 000 ) surface (the C-face) and the (0001) surface (the Si-face) of SiC, by annealing in ultra-high vacuum or in an argon environment, is studied by atomic force microscopy (AFM) and low-energy electron microscopy (LEEM). The graphene forms due to preferential sublimation of Si from the surface. In vacuum, this sublimation occurs much more rapidly for the C-face than the Si-face, so that 150°C lower annealing temperatures are required for the C-face to obtain films of comparable thickness. The evolution of the morphology as a function of graphene thickness is examined, revealing significant differences between the C-face and the Si-face. For annealing near 1320°C, graphene films of about 2 monolayers (ML) thickness are formed on the Si-face, but 16 ML is found for the C-face. In both cases, step bunches are formed on the surface and the films grow continuously (carpet-like) over the step bunches. For the Si-face in particular, layer-by-layer growth of the graphene is observed in areas between the step bunches. At 1170°C, for the C-face, a more 3-dimensional type of growth is found. The average thickness is then about 4 ML, but with a wide variation in local thickness (2 -7 ML) over the surface. The spatial arrangement of constant-thickness domains are found to be correlated with step bunches on the surface, which form in a more restricted manner than at 1320°C. It is argued that these domains are somewhat disconnected, so that no strong driving force for planarization of the film exists. In a 1-atm argon environment, permitting higher growth temperatures, the graphene morphology for the Si-face is found to become more layer-by-layer-like even for graphene thickness as low as 1 ML. However, for the C-face the morphology becomes much worse, with the surface displaying markedly inhomogeneous nucleation of the graphene. It is demonstrated that these surfaces are unintentionally oxidized, which accounts for the inhomogeneous growth.

Low-energy electron reflectivity from graphene: First-principles computations and approximate models

“…by acquiring a sequence of images at different energies) permit detailed mapping of the graphene thickness. Such measurements have been pursued for graphene on SiO 2 [2], on SiC [3,4,5] and on various metal substrates [6,7,8]. In two recent papers, we have argued that the oscillations in the reflectivity spectra from graphene permit not only the determination of the thickness of the multilayer graphene, but they also can yield information about the interface between the graphene and the substrate that it resides on [9,10].…”

Characterizations of as grown and functionalized epitaxial grapheneg rown on SiC surfaces

“…the existence a rotational disorder between adjacent layers. Several later investigation [64][65][66][67][68][69] favored the latter explanation, i.e. existence of rotational disorder between adjacent layers in the domains/grains.…”

CVD formation of graphene on SiC surface in argon atmosphere

“…Preparation of pure, good quality, and large graphene wafers is of main technological interest. For many years, the SiC surfaces have been used for the graphene sheets growth in the epitaxy process by the Si sublimation 9 . This method, however, introduces many defects and causes that graphene does not possess satisfactory electronic transport properties.…”