Simultaneous observation of oxygen uptake curves and electronic states during room-temperature oxidation on Si(001) surfaces by real-time ultraviolet photoelectron spectroscopy

摘要

Ultraviolet photoelectron spectroscopy was used to measure the oxygen uptake, changes in work function due to the surface dipole layer of adsorbed-oxygen atoms, Δφ_(SDL), and changes in band bending due to the defect-related midgap state, ΔBB, simultaneously during oxidation on Si(001) surface at room-temperature, RT, under an O_2 pressure of 1.3 × 10~(-5) Pa. The oxygen dosage dependence of Δφ_(SDL) revealed that dissociatively adsorbed-oxygen atoms occupy preferentially dimer backbond sites at the initial stage of Lang-muir-type adsorption, which is associated with a rapid increase of ΔBB. When raising temperature to ～600 ℃, such preferential occupation of the dimer backbond sites by oxygen atoms is less significant and ΔBB becomes smaller in magnitude. The observed relation between Δφ_(SDL) 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 ℃.