Chemisorption of O-2 and CO on the K-modified diamond (100) 2 X 1 surface

The adsorption of O-2 and CO molecules on the K-modified C(100) surface has been studied mainly by electron energy loss spectroscopy (EELS) and additi onally by thermal desorption spectroscopy (TDS) and low-energy electron dif fraction (LEED) at 300 K. Although O-2 does not react with the clean C(100) surface, it readily reacts with the K-modified surface. The adsorbed speci es are characterized by the two loss peaks at 150 and 214 meV. The 150 and 214-meV losses are ascribed to the C - O stretch of the C-O-C (ether) and > C = O (carbonyl) species which are formed by breaking both sigma and pi bo nds of a surface dimer, respectively. In contrast to Si(100), substrate oxi dation mainly occurs at the top layer of C(100)). The CO molecule also reac ts with the K-modified surface, while it does not react with the clean C(10 0) surface. The adsorbed species are characterized by the loss peaks at 154 meV with a shoulder at 192 meV. The 154-meV loss is tentatively assigned t o the C - O stretch of the (C2O2)(2-) 2K(+) complex formed on the K-modifie d C(100) surface. The shoulder at 192 meV is ascribed to the C - O stretch of either (C4O4)(2-) 2K(+) or > C = O, in which the pi bond is largely pert urbed by the K adatoms. (C) 2001 Elsevier Science B.V. All rights reserved.