Spin and alignment effects in O2chemisorption on Fe(110), Ni(111), and Co(0001) films grown on W(110)

Abstract

O2 has a spin triplet multiplicity in its ground state, while the effect of its electron spin on O2-surface interaction is not well understood. In this study, the spin and/or alignment effects in O2 chemisorption on surfaces of Fe(110), Ni(111), and Co(0001) films grown on W(110) have been investigated with the use of a single spin-rotational state-selected O2 beam. The results indicate that the spin effects for the Fe and Ni films are similar in that the initial sticking probability (S0) of O2 is higher when the spins of O2 and the film are antiparallel, and the spin dependence in S0, which amounts to 30%-40% at thermal energy, decays with increasing the O2 kinetic energy (E0). In the case of the Fe/O2 system, however, considerable spin dependence was found to remain even at E0 > 0.2 eV and on the oxidized surface. It has also been shown that the barrier for O2 chemisorption increases in the order of Fe(110) < Ni(111) < Co(0001), and the difference in the observed alignment effect among the samples can be understood based on the difference in the barrier.