Simultaneous observation of oxygen uptake curves and electronic states during room-temperature oxidation on Si(0 0 1) surfaces by real-time ultraviolet photoelectron spectroscopy

Ultraviolet photoelectron spectroscopy was used to measure the oxygen uptake, changes in work function due to the surface dipole layer of adsorbed-oxygen atoms, ΔϕSDL, and changes in band bending due to the defect-related midgap state, ΔBB, simultaneously during oxidation on Si(0 0 1) surface at room-temperature, RT, under an O2 pressure of 1.3 × 10−5 Pa. The oxygen dosage dependence of ΔϕSDL revealed that dissociatively adsorbed-oxygen atoms occupy preferentially dimer backbond sites at the initial stage of Langmuir-type adsorption, which is associated with a rapid increase of ΔBB. When raising temperature to ∼600 °C, such preferential occupation of the dimer backbond sites by oxygen atoms is less significant and ΔBB becomes smaller in magnitude. The observed relation between ΔϕSDL and ΔBB indicates that point defects (emitted Si atoms + vacancies) are more frequently generated by oxygen atoms diffusing to the dimer backbond sites at lower temperature in RT −600 °C.