Abstract
A study of the semiconductor-metal transition in the series , x=0.0–0.4, using electron-spectroscopy techniques is presented. The results show that the ground state of has strongly mixed character. From the experiments we estimate the on-site Coulomb correlation energies and to be 3.4 and 6.7 eV, respectively, while the () interaction strength is 2.2 eV. A comparison of the experiment with the results of a model many-body cluster calculation for the Co 2p spectra indicates a low-spin state of Co in . The band gap of is estimated to be about 0.6 eV from ultraviolet photoemission spectroscopy and bremsstrahlung isochromat spectroscopy measurements. The semiconductor-metal transition results from overlap of doped hole states with the valence band for x≥0.2.
- Received 13 July 1992
DOI:https://doi.org/10.1103/PhysRevB.46.9976
©1992 American Physical Society