Hole-doping-induced changes in the electronic structure of La1-xSrxFeO3: Soft x-ray photoemission and absorption study of epitaxial thin films

We have studied the electronic structure of epitaxially grown thin films of La1-xSrxFeO3 by in situ photoemission spectroscopy (PES) and x-ray-absorption spectroscopy (XAS) measurements. The Fe 2p and valence-band PES spectra and the O 1s XAS spectra of LaFeO3 have been successfully reproduced by configuration-interaction cluster-model calculation and, except for the satellite structure, by band-structure calculation. From the shift of the binding energies of core levels, the chemical potential was found to be shifted downward as x was increased. Among the three peaks in the valence-band spectra of La1-xSrxFeO3, the peak nearest to the Fermi level (E-F), due to the e(g) band, was found to move toward E-F and became weaker as x was increased, whereas the intensity of the peak just above E-F in the O 1s XAS spectra increased with x. The gap at E-F was seen for all values of x. These results indicate that changes in the spectral line shape around E-F are dominated by spectral weight transfer from below to above E-F across the gap and are therefore highly nonrigid-bandlike changes.