Role of structure of C-terminated4H-SiC(0001¯) surface in growth of graphene layers: Transmission electron microscopy and density functional theory studies

Abstract

Principal structural defects in graphene layers, synthesized on a carbon-terminated face, i.e. the SiC(0001 ) face of a 4H-SiC substrate, are investigated using microscopic methods.Results of high-resolution transmission electron microscopy (HRTEM) reveal their atomic arrangement. Mechanism of such defects creation, directly related to the underlying crystallographic structure of the SiC substrate, is elucidated. The connection between the 4H-SiC(0001 ) surface morphology, including the presence of the single atomic steps, the sequences of atomic steps, and also the macrosteps, and the corresponding emergence of planar defective structure (discontinuities of carbon layers and wrinkles) is revealed. It is shown that disappearance of the multistep island leads to the creation of wrinkles in the graphene layers. The density functional theory (DFT) calculation results show that the diffusion of both silicon and carbon atoms is possible on a Si-terminated SiC surface at a high temperature close to 1600°C. The creation of buffer layer at the Si-terminated surface effectively blocks horizontal diffusion, preventing growth of thick graphene layer at this face.At the carbon terminated SiC surface, the buffer layer is absent leaving space for effective horizontal diffusion of both silicon and carbon atoms. DFT results show that excess carbon atoms converts a topmost carbon layer to sp 2 bonded configuration, liberating Si atoms in a) Electronic mail: jolanta.borysiuk@fuw.edu.pl 2 barrierless process. The silicon atoms escape through the channels created at the bending layers defects, while the carbon atoms are incorporated into the growing graphene layers.These results explain growth of thick graphene underneath existing graphene cover and also the creation of the principal defects at the C-terminated SiC(0001) surface.

Interface disorder probed at the atomic scale for graphene grown on the C face of SiC

“…The picture is not equally clear for graphene grown on the C face. Apart from a general acceptance of a weaker interface coupling with respect to the Si face [16,17], uncertainty still exists on whether graphene * antonino.lamagna@imm.cnr.it grows directly on the C-terminated surface [18,19] or if it is preceded by either ordered surface reconstructions [16] or a disordered/amorphous interface layer [20][21][22]. Further dispute exists on whether the formation of graphene on the C face is driven by an epitaxial process, as the presence of domains with different orientations and numbers of graphene layers indicates the possible suppression of related mechanisms.…”

Structural investigations of hydrogenated epitaxial graphene grown on 4H-SiC (0001)

“…It can be assumes that a graphene stack grows as a thin film parallel to the local SiC substrate planes and follows the local morphology of the SiC surface, which was already shown in TEM experiments. [20][21][22][23] In the case of the on-axis SiC (0001) substrates, one can expect surface steps originating from substrate etching in a hydrogen atmosphere. 24 We should expect a diffraction pattern composed of SiC scattering and graphene stack scattering but with the graphene scattered intensity many orders of magnitude lower than SiC X-ray reflections (Fig.…”

Effect of Residual Gas Composition on Epitaxial Growth of Graphene on SiC

“…Firstprinciples calculations has been done to study graphene buffer layer formation on SiC(0001), diffusion of carbon on SiC [6], stability and reactivity of atomic steps of SiC in the initial graphene growth stage [7]. Experimental studies have been done to understand mechanisms of epitaxial graphene growth on SiC(0001) [8], SiC(0001) [9], non-polar SiC surfaces [10] and to elucidate role of carbon diffusion [11] and silicon sublimation [9]. It has been shown that graphene with reduced pit density can be grown on nominally flat SiC substrates [9] and graphene quality can be further improved when grown in high argon pressure [12].…”