Photoemission study of metastable oxygen adsorbed on a Si(111)-(7×7) surface

We have investigated the metastable oxygen species adsorbed on a Si(111)-(7×7) surface at room temperature using real time valence-band and core-level photoemission measurements. The dosage- and time-dependent changes in the intensity of the metastable 3.8 eV peak observed in the valence-band spectra were different from those of the metastable O 1s components. Further, although no metastable O 1s components were observed in the core-level measurement after annealing the sample at 600 K, the 3.8 eV peak was still observed. These results indicate that both the stable and the metastable oxygen species produce the 3.8 eV valence-band peak, and we therefore conclude that the contradicting lifetimes reported in the literature result from a misinterpretation of the 3.8 eV peak