UV-induced formation of oxygen-derived dangling bonds on hydroxyl-terminated SiC

• Published in: Journal of physics. Condensed matter Vol. 30; no. 43; p. 435002
• Main Authors: Aghdassi, Nabi, Krüger, Peter, Linden, Steffen, Dulson, Dorothea, Zacharias, Helmut
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 31.10.2018
• Subjects: electronic surface band structure; hydroxyl termination; photoelectron spectroscopy; self-interaction-corrected pseudopotentials; silicon carbide; surface dangling bonds
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/1361-648X/aae2cc

A combined theoretical and multi-technique experimental study was employed to comprehensively determine the electronic structure of 6H-SiC(0 0 0 1) surfaces upon hydroxyl and oxygen termination. We demonstrate the UV-induced formation of single-coordinated oxygen radicals in on-top sites above the atoms of the uppermost silicon layer of the substrate on initially hydroxyl-terminated SiC. Such a configuration of oxygen radicals represents an unprecedented adsorbate-derived system of unpaired electrons, bearing analogy to silicon and carbon dangling bonds on clean, unreconstructed SiC surfaces. We evidence the presence of adsorbate-derived surface states within the fundamental band gap for both hydroxyl- and oxygen-terminated SiC. For hydroxyl termination, a hydrogen-induced unoccupied surface state is revealed consistently by inverse photoemission spectroscopy and density-functional theory calculations employing self-interaction-corrected pseudopotentials (DFT-SIC). The formation of oxygen dangling bonds is accompanied by the occurrence of an occupied surface state derived from px- and py-orbitals associated with the unpaired electrons as proven by both ultraviolet photoemission spectroscopy and DFT-SIC.