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

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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 (EF), due to the ``eg band'', was found to move toward EF and became weaker as x was increased, whereas the intensity of the peak just above EF in the O 1s XAS spectra increased with x. The gap or pseudogap at EF was seen for all values of x. These results indicate that changes in the spectral line shape around EF are dominated by spectral weight transfer from below to above EF across the gap and are therefore highly non-rigid-band-like.