The oxidation of potassium on MgO(100)

The interaction of oxygen and potassium on MgO(100) has been studied using thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The results show that several oxygen species are present on the surface. An atomic oxygen species is initially present at lower theta(K) as shown by the evidence of O 1s BE at 528.5 eV, together with the consistent but not coincident desorption of potassium and oxygen at 610 and 525 K, respectively. The oxygen desorption at a low temperature of 425 K coupled with the O 1s BE at 532.1 eV indicates the associative molecular oxygen adsorption on oxygen vacancies in the substrate. The non-stoichiometric 3D K-O clusters form on the surfaces for theta(K)>1 ML. The desorption of K2O2 followed by K2O at similar to 600 K was observed. (C) 1998 Elsevier Science B.V.