The depth sensitivity of spectroscopic ellipsometry (SE) to the presence of oxygen vacancies (V Ö), in perovskite titanates, was examined over the wavelength range from 250 to 750 nm. To determine the effect of oxygen vacancy concentration, reference optical properties of barium titanate (BaTiO 3) and Fe-doped SrTiO 3 were determined for oxidized and reduced samples. These reference data were used to model the sensitivity of SE to changes due to degradation. Using these models, it was found that SE could detect reduced layers of 4 Å for BaTiO 3 and an 8 Å layer for Fe-doped SrTiO 3. From the models, concentration gradients were resolvable by SE with an average diffusion depth (√Dt) of 10 Å for BaTiO 3 and 50 Å for Fe-doped SrTiO 3. These models also predict that SE should be able to discern different degradation mechanisms through the way the optical properties change during degradation.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites