Carbon-Based Aromatic-Like Nanostructures on the Vicinal SiC Surfaces Induced by Ba Adsorption

Abstract

The electronic structure of the SiC/Si(111)-8° and SiC/Si(111)-4° epitaxial layers with adsorbed Ba submonolayers is thoroughly studied in situ in ultrahigh vacuum by synchrotron-based photoemission spectroscopy. The SiC epitaxial layers were grown on the vicinal Si(111)-8°, Si(111)-4° surfaces by the original method of substitution of atoms. The C 1s and Si 2p сore level spectra are investigated in relation to the different Ba coverages. A substantial change in the C 1s spectra induced by Ba adsorption is revealed. It is found that the effect results from the formation of a new, previously unknown carbon-based structure consist of nanoclusters on the surface. Experimental data show that the nanoclusters can be created exclusively on the vicinal SiC surfaces in the presence of stabilizing adsorbed metal atoms, specifically, Ba atoms. Density functional theory using the basis of plane waves with the pseudopotential approximation is applied to calculate the spatial configuration of this clusters structure. It is shown that the surface nanoclusters are formed due to local interaction between silicon vacancies, carbon atoms and Ba adatoms. It is established that the carbon clusters is composed of carbon rings, in which the chemical bonds are close in nature to the bonds inherent in aromatic-like compounds.