Synchrotron radiation photoemission study of Ba adsorption on the vicinal SiC(111)-8° surface

Abstract

The electronic structure of the Ba/SiC(111)-8° interface has been studied in detail in situ in an ultrahigh vacuum using synchrotron radiation photoelectron spectroscopy. The SiC(111)-8° samples were grown by an original method of epitaxy of low-defect unstressed nanoscaled silicon carbide films on silicon substrates. The Si 2p, C 1s core level spectra have been investigated as a function of Ba submonolayer coverage with photon energies in the range of 100–450 eV. Upon Ba adsorption, a drastic change in the C 1s spectrum was revealed. It was found that Ba adsorption leads to the formation of a new, previously unknown carbon-based structure of C nanoclusters on the surface. Experimental data show that the nanoclusters can be created exclusively on the vicinal SiC(111)-8° surfaces in the presence of stabilizing adsorbed metal atoms, specifically, Ba atoms. It is shown that the surface nanoclusters are formed due to the local interaction between silicon vacancies, carbon atoms and Ba adatoms. It is established that the carbon clusters are composed of carbon rings and their chemical bonds are similar in nature to the bonds in aromatic-like compounds.