Photoemission studies of Titanium Oxides

Titanium exposed to dry air at varying temperatures are studied by X-ray photoelectron spectroscopy (XPS) in combination with low energy Ar ion sputtering. The 2 nm deposit formed at room temperature in 30^d is an oxide mixture with chiefly Ti₂O₃. This result is indicated by the Ti(2p) level binding energy, FWHM and asymmetry. The dry air exposures at high temperatures resulted in oxide species of nonstoichiometric TiO_2–x. As proposed from sputtering effects to XP-spectra the oxygen deficient TiO_2–x surface region includes Ti³⁺-interstitials. These interstitials act as donors (emission to (3d)-states) and hinder the oxygen diffusion via interstitials (temperature: ≦ 550 °C). It is to be noted that electron emission from donor states is favoured in deeper lying (2p)-states by decreasing concentration of oxygen vacancies.