Real-time monitoring of oxidation on the Ti(0 0 0 1) surface by synchrotron radiation photoelectron spectroscopy and RHEED–AES

The oxidation kinetics on the Ti(0 0 0 1) single crystal surface was investigated by real-time Auger electron spectroscopy combined with reflection high-energy electron diffraction (RHEED–AES) and high-resolution photoelectron spectroscopy using synchrotron radiation. The RHEED specular reflection spot intensity showed an oscillatory behavior, at the maxima and minima of which the oxygen uptake curve obtained by O KLL Auger electron intensity shows breaks. This agreement indicates that growth of oxides progresses with changing the surface morphology and the oxygen uptake rate. The O2 dose dependence of Ti 2p photoelectron spectrum measured at photon energies of 574.6 eV (surface sensitive) and 1549 eV (bulk sensitive) revealed that (1) oxidation of metallic Ti atoms with growing Ti2O and TiO on the surface makes the surface morphology roughened up to ∼17 L; (2) the roughened morphology is recovered by oxidation of Ti2O and TiO into Ti2O3, Ti3O5 and TiO2 up to ∼45 L; (3) after almost saturation of TiO2 growth in the surface layer the surface morphology is roughened again by further oxidation at the interface up to ∼140 L; and (4) then the oxygen uptake rate is considerably suppressed due to the passivation effect of grown oxides.