Anodized titanium oxide thickness estimation with ellipsometry, reflectance spectra extrema positions and electronic imaging: importance of the interfaces electromagnetic phase-shift

•The oxide thickness is obtained from reflectance spectra extrema.•The oxide thickness is measured also with ellipsometry and electronic images.•Neglecting the interfaces phase-shift can induce errors of 50% on the thickness.•The phase-shift has a significant impact for oxide layers thinner than 50 m.