Electron spectroscopic investigation of metal-insulator transition in Ce1-xSrxTiO3

We have carried out detailed electron spectroscopic investigation of Ce1- xSrxTiO3 exhibiting insulator-metal transition with x. Core level X-ray photoelectron spectra of Ce 3d as well as resonant photoemission spectra obtained at the Ce 4 d → 4f resonant absorption threshold establish Ce as being in the trivalent state throughout the series. Using the 'off-resonance' condition for Ce 4f states, we obtain the Ti 3 d dominated spectral features close to EF, exhibiting clear signatures of coherent and incoherent peaks. We discuss the implications of our find ings in relation to the metal - insulator transition observed in this series of compounds.