(a) upper part: LaAlO3/SrTiO3 XAS Ti L spectra for 5 u.c. and 1 u.c. samples taken in TEY. Difference spectra between thick and thin LaAlO3/SrTiO3 ((a) lower part), LaGaO3/SrTiO3 (b) and NdGaO3/SrTiO3 (c) samples taken in different yield modes and compared to the simulated Ti3+ spectra. The vertical axis for the difference spectra is always the same.