CHEMICAL-CHANGES INDUCED BY SPUTTERING IN TIO2 AND SOME SELECTED TITANATES AS OBSERVED BY X-RAY-ABSORPTION SPECTROSCOPY

We studied the chemical changes induced by Ar+-bombardment in TiO2 and some selected titanates by means of soft X-ray absorption spectroscopy. The O 1s and Ti 2p spectra provide unique information on hybridization, valency and crystal-field effects. In TiO2, we found that some Ti ions are partly reduced but no metallization is observed. On the other hand, the effect of ion-bombardment in titanates depends on the counter-ions. In Al2TiO5, the central Ti ions are strongly reduced while Al2O3 remains unaffected. In NiTiO3, by contrast, we found the opposite behaviour with strong reduction of the counter Ni ions. This contrasting behaviour seems to be related to differences in the relative heat of formation of the sub-species. In PbTiO3, both central- and counter-ions are affected by sputtering. Finally, the electronic structure of BaTiO3 presents very little change s upon ion-bombardment.