Comparison of Ti 2p Core-Level Peaks from TiO2, Ti2O3, and Ti Metal, by XPS

These spectra compare the Ti 2p core-level XPS line shape for atomically clean, stoichiometric samples of Ti, Ti2O3, and TiO2; the latter two are UHV-cleaved or fractured single crystals. The Ti0 and Ti4+ peaks of Ti metal and TiO2, respectively, exhibit the simple shapes expected for such core levels. The Ti3+ peaks of Ti2O3, however, are more complex, although there are no other valence states of Ti in the sample.