Initial Stages of the Graphite-SiC(0001) Interface Formation Studied by Photoelectron Spectroscopy

Abstract

Graphitization of the 6H-SiC(0001) surface as a function of annealing temperature has been studied by ARPES, high resolution XPS, and LEED. For the initial stage of graphitization – the 6√3 reconstructed surface – we observe σ-bands characteristic of graphitic sp2-bonded carbon. The π-bands are modified by the interaction with the substrate. C1s core level spectra indicate that this layer consists of two inequivalent types of carbon atoms. The next layer of graphite (graphene) formed on top of the 6√3 surface at TA=1250°C-1300°C has an unperturbed electronic structure. Annealing at higher temperatures results in the formation of a multilayer graphite film. It is shown that the atomic arrangement of the interface between graphite and the SiC(0001) surface is practically identical to that of the 6√3 reconstructed layer.

Experimental studies of the electronic structure of graphene

“…interpret the (6√3 x 6√3)R30° phase on the basis of these findings as a single, graphene-like layer with an intact in-plane, σ-type bonding, but in which a strong interaction with the p z orbitals and the SiC substrate occurs [55]. This layer is devoid of states at the Fermi level and thus acts as passivation layer for the SiC substrate, such that subsequently growing layers exhibit properties which appear, except for the doping discussed below, practically identical to exfoliated single and few layer graphene.…”

“…Since the barrier for electrons on 6H-SiC(0001) is rather small (0.3±0.1 eV), and the valence band offset between different SiC polytypes is basically zero, the authors estimate that this barrier is increased by 0.3 eV to 0.6±0.1 eV when using n-type 4H-SiC(0001). The Schottky barrier is also strongly face specific [55], being much larger (1.4 eV) on the C-face of n-type 6H-SiC than on the Si face, a fact which demonstrates the influence of the difference in the dipole layer on these surfaces. This could be an advantage of graphene on carbon-terminated SiC phase to the first graphene layer [55].…”

“…under clean and controlled conditions, and using epitaxial graphene on substrates such as silicon carbide or metals [3,33,[51][52][53][54][55].…”

“…The low energy electron diffraction (LEED) patterns corresponding to this sequence of preparation steps is shown in Figure 2. The second method relies on ex-situ etching of the SiC substrates in a stream of hydrogen [33,35,47,55,64]. This results in surfaces which are covered by a silicate adlayer [65].…”

“…For a use in devices, the band alignment and transport barriers between epitaxial graphene and the silicon carbide substrate need to be known. Such information has also been obtained from core level spectroscopy [47,78] for few layer graphene on n-and p-type SiC, and for n-type for the silicon and carbon-terminated [55]. Since the barrier for electrons on 6H-SiC(0001) is rather small (0.3±0.1 eV), and the valence band offset between different SiC polytypes is basically zero, the authors estimate that this barrier is increased by 0.3 eV to 0.6±0.1 eV when using n-type 4H-SiC(0001).…”