Figure 2

Ti-L_2,3 edge EELS taken at the LaAlO₃/SrTiO₃ interface.

EELS spectrum at the interface of the (a) 3 u.c. (b) 5 u.c. sample. The contributions of Ti⁴⁺ and T³⁺ to the Ti edge were deduced from a linear combination of two reference spectra, a green one for Ti⁴⁺ (SrTiO₃ away from the interface of the (a) 3 u.c. (b) 5 u.c. sample) and a red one Ti³⁺ (Bulk Ti₂O₃) recorded on the same spectrometer. The method of least squares has been used to fit the experimental and the simulation spectra. The blue dots spectra correspond to the experimental EELS measurement at the very first unit cell below the interface. The black curves represent the best simulation that fitted the experimental spectrum. One observes that the Ti oxidation state is quite similar between the conductive and insulating samples grown in the same conditions.