Chemisorbed states of atomic oxygen and its replacement by atomic hydrogen on the diamond (100)-(2 x 1) surface

The chemisorbed states of atomic oxygen and the subsequent replacement of the adsorbed O atoms by atomic hydrogen on the C(100) surface have been studied by electron energy loss spectroscopy (EELS), thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED). EELS spectra of the O-adsorbed C(100) surface at 300 K show losses at 113, 150, 215 and 261 meV. The 113 and 215 meV losses are assigned as the bending and stretching modes of the surface carbonyl (drop C=O) species (on-top O), respectively, which is formed by the dimer pi- and sigma-bond breaking. The 150 meV loss is attributed to the surface ether (C-O-C) species (bridging O) which is also formed by the dimer bond breaking. These species are desorbed as CO at similar to 1100 K. The 261 meV loss indicates the existence of minority O atoms nearly triple-bonded to the substrate (which is decomposed by heating up to 800 K). When the O-preadsorbed C(100) surface is exposed to an increasing amount of H, the 215 meV loss disappears and losses appear at 104, 152 and 362 meV which are associated with the surface hydride species. No CO and CO, desorptions are observed. These results suggest that the surface O atoms are replaced by atomic H completely and hydride species are formed. A model for the replacement is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.