Oxygen-induced surface state on diamond (100)

Abstract

Abstract The electronic structure of oxygenated diamond (100) surface is studied comparatively by experimental photoemission techniques and first principles calculations. Controlled oxygenation of the diamond (100) 2×1 surface at 300°C yields a smooth O:C (100) 1×1 surface with a distinctive emission state at ∼3 eV from the Fermi edge. Oxygenation of the hydrogenated surface at temperatures above 500°C, however, gives rise to extensive etching and roughening of the surface. The experimentally observed emission state at ∼3 eV following O adsorption is assigned to the O-induced surface state. When the oxygenated surface is annealed to 800°C to desorb chemisorbed O, the surface structure changes from 1×1 to 2×1 and another surface state emission at 2.5 eV associated with the clean surface reconstruction can be observed by UPS. This is attributed to the π-bond reconstruction of sub-surface carbon layers following the desorption of first layer CO from the surface. To understand the origin of the O-induced emission state, we calculated the density of states (DOS) of the oxygenated diamond using the first principles linear muffin-tin orbital (LMTO) method with atomic sphere approximation (ASA) based on density functional theory (DFT) and local density approximation (LDA).