Electronic properties of the Cs and O co-adsorption on Mo(100) at room temperature

Room-temperature co-adsorption of Cs and O 2 on Mo(100) is studied by ELS, UPS and work function changes. The authors use a constant amount of caesium (4.3*10 14 atoms cm -2 ) which corresponds to a monolayer on clean Mo(100). The loss peak at 1.65 eV observed for the Cs monolayer disappears for an oxygen exposure L of 0.28 L (Langmuir) and is replaced by a loss peak at 1.2 eV. Both losses are attributed to interband transitions. Above 2 L several O2p states are observed in UPS, indicating that O is bonded to the substrate and to the Cs. These spectra differ significantly from those obtained for Cs deposited on an Mo surface with various oxygen coverages. The differences observed with respect to Cs on Cu(111) are attributed to a substrate effect.