188
9 Hybridized Bonding
Fig. 9.6 ARPES from the clean Rh(001) (dotted curves) and Rh(001(2 × 2)-S (solid curves)
surfaces. The parallel momenta k // shown are calculated for electrons emitted from the Fermi level.
Data were collected a along the M <10> and b the X <11> direction. Reprinted with permission
from [51]
9.3 Coverage Resolved O–Cu Valence DOS Evolution
The O-coverage-resolved PES (He-II, 21.22 eV), see Fig. 9.7, revealed that oxidation
of a polycrystal copper surface proceeds in three stages [9]:
• Firstly (the lowest, 12 L, exposures), oxidation begins, which immediately raises
a spectral shoulder at −1.5 eV for nonbonding states and a small peak at −6.0 eV
for O–Cu bonding states. The emergence of the new DOS features is at the expense
of a sharp fall of the DOS features between −3.0 eV and E F as an indication of
Cu
+ hole production.
• Secondly (12 ~ 1000 L), both the −6.0 eV DOS feature and the sharp-fall at E F >
E > −3.0 eV become pronounced as the oxygen exposure increases as the number
of the O–Cu bond grows with charge transporting from Cu to O.