Oxygen-induced surface state on diamond (100)

The electronic structure of oxygenated diamond (100) surface is studied com paratively by experimental photoemission techniques and first principles ca lculations. Controlled oxygenation of the diamond (100) 2 x 1 surface at 30 0 degreesC yields a smooth O:C (100) 1 x 1 surface with a distinctive emiss ion state at similar to3 eV from the Fermi edge. Oxygenation of the hydroge nated surface at temperatures above 500 degreesC, however, gives rise to ex tensive etching and roughening of the surface. The experimentally observed emission state at similar to3 eV following O adsorption is assigned to the O-induced surface state. When the oxygenated surface is annealed to 800 deg reesC to desorb chemisorbed O, the surface structure changes from 1 x 1 to 2 x 1 and another surface state emission at 2.5 eV associated with the clea n surface reconstruction can be observed by UPS. This is attributed to the pi -bond reconstruction of sub-surface carbon layers following the desorpti on of first layer CO from the surface. To understand the origin of the O-in duced emission state, we calculated the density of states (DOS) of the oxyg enated diamond using the first principles linear muffin-tin orbital (LMTO) method with atomic sphere approximation (ASA) based on density functional t heory (DFT) and local density approximation (LDA). (C) 2001 Elsevier Scienc e B.V. All rights reserved.