The Oxygen K edge in Strontium Titanate and Lanthanum Titanate
Microscopy and Microanalysis
Recently there has been considerable interest in titanates for applications in electronic components such as varistors, and as candidates for high dielectric constant materials to replace silicon dioxide in MOS transistors. Superlattices composed of strontium and lanthanum titanate layers should show one dimensional charge modulation due to the formal change in valence from 4+ in SrTiO 3 to 3+ in LaTiO 3 . Multilayers grown by pulsed laser deposition have been examined by a combination of high
... ngle annular dark field imaging and electron energy loss spectrometry  . The titanium L 23 edges the lanthanum M 45 edge and the oxygen K edge were all recorded with an energy resolution of about 0.9eV and a spatial resolution of about 1.9 Å. The titanium L 23 near edge structure can be decomposed into a linear combination of the spectra from Ti 3+ and Ti 4+ and can be well modeled using atomic multiplet theory  . This is because the octahedral symmetry at the Ti site is preserved, any change in valence is accommodated at the Ti site, and the Ti 2p-3d-3d couplings in the presence of a core hole are large compared with the width of the 3d bands.