THE OXIDATION OF POTASSIUM ON MGO(100)

The interaction of oxygen and potassium on MgO(100) has been studied u sing thermal desorption spectroscopy (TDS) and X-ray photoelectron spe ctroscopy (XPS). The results show that several oxygen species are pres ent on the surface. An atomic oxygen species is initially present at l ower theta(K) as shown by the evidence of O 1s BE at 528.5 eV, togethe r with the consistent but not coincident desorption of potassium and o xygen at 610 and 525 K, respectively. The oxygen desorption at a low t emperature of 425 K coupled with the O 1s BE at 532.1 eV indicates the associative molecular oxygen adsorption on oxygen vacancies in the su bstrate. The non-stoichiometric 3D K-O clusters form on the surfaces f or theta(K)>1 ML. The desorption of K2O2 followed by K2O at similar to 600 K was observed. (C) 1998 Elsevier Science B.V.