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 4d arrow4f 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 3d dominated spectral features close to EF, exhibiting clear signatures of coherent and incoherent peaks. We discuss the implications of our findings in relation to the metal– insulator transition observed in this series of compounds.