Electron-spectroscopy study of the semiconductor-metal transition in La1-xSrxCoO3.

摘要: A study of the semiconductor-metal transition in series ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CoO}}_{3}$, x=0.0\char21{}0.4, using electron-spectroscopy techniques is presented. The results show that ground state ${\mathrm{LaCoO}}_{3}$ has strongly mixed character. From experiments we estimate on-site Coulomb correlation energies ${\mathit{U}}_{\mathit{d}\mathit{d}}$ and ${\mathit{U}}_{\mathit{p}\mathit{p}}$ to be 3.4 6.7 eV, respectively, while (${\mathit{pd}}_{\mathrm{\ensuremath{\sigma}}}$) interaction strength 2.2 eV. comparison experiment with a model many-body cluster calculation for Co 2p spectra indicates low-spin ${\mathrm{LaCoO}}_{3}$. band gap estimated about 0.6 eV from ultraviolet photoemission spectroscopy bremsstrahlung isochromat measurements. overlap doped hole states valence x\ensuremath{\ge}0.2.