Temperature dependence of oxidation-induced changes of work function on Si(001)2 × 1 surface studied by real-time ultraviolet photoelectron spectroscopy

At the initial stage of oxidation on a Si(001)2 × 1 surface, real-time ultraviolet photoelectron spectroscopy revealed that the O ₂ dosage dependences of band bending and work function due to a surface dipole layer show a distinct change with increasing temperature from 300 to 600°C in a Langmuir-type adsorption region, while oxygen uptake curves are almost the same at all temperatures examined. In constant to a dual-oxide-species (DOS) model in which the surface migration of adsorbed oxygen is not considered for Langmuir-type adsorption, the observed changes in work function due to the surface dipole layer mean that adsorbed oxygen can migrate on the surface more frequently with increasing temperature, leading to a decrease in the number of adsorbed oxygen atoms bonded at dimer backbond centers and furthermore a significant structural change of the oxide layer.