Diffusion of oxygen on tungsten (110)

The surface diffusion of oxygen on W(110) was studied in the temperature range 760-8800C and for coverages up to one monolayer. Coverage-distance plots after diffusion runs were determined via corresponding work function profiles measured by a newly developed, laterally resolving vibrating capacitor method. The coverage profiles were evaluated in terms of a concentration dependent diffusion coefficient (DC) using the Boltzmann-Matano analysis. The temperature dependence of the DC can be described by a constant activation energy of 27+-2 kcal/mole in the coverage range 0.4 < theta < 0.9. The concentration dependence of the DC shows a maximum near theta = 0.45 and a decrease beyond theta = 0.6. This behavior is correlated with observed LEED structures and interpreted by a rather abrupt change of the chemical potential near theta = 0.5 and a decreasing hopping probability for higher coverages. (Auth.)