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

The chemisorbed states of atomic oxygen and the subsequent replacement of t he adsorbed O atoms by atomic hydrogen on the C(100) surface have been stud ied by electron energy loss spectroscopy (EELS), thermal desorption spectro scopy (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 me V. The 113 and 215 meV losses are assigned as the bending and stretching mo des of the surface carbonyl (drop C=O) species (on-top O), respectively, wh ich 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 sim ilar to 1100 K. The 261 meV loss indicates the existence of minority O atom s 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 increasin g amount of H, the 215 meV loss disappears and losses appear at 104, 152 an d 362 meV which are associated with the surface hydride species. No CO and CO, desorptions are observed. These results suggest that the surface O atom s are replaced by atomic H completely and hydride species are formed. A mod el for the replacement is proposed. (C) 1999 Elsevier Science B.V. All righ ts reserved.