Abstract
(0.10≤x≤0.40) polycrystalline samples have been studied by x-ray diffraction, resistivity and Hall-coefficient measurements, x-ray and ultraviolet photoemission spectroscopy, and inverse-photoemission spectroscopy (IPES). The lattice constant of the c axis decreases and that of the a(b) axis increases as a function of x. The results of Hall-coefficient measurements indicate that hole concentration is reduced as a function of x, which is consistent with the results of oxygen-concentration measurements. We find no energy shifts of the core levels, valence bands, and conduction bands for the samples, which is completely different from the results for the system. The results of IPES and resistivity measurements show that the metal-semiconductor transition occurs at about x=0.35. The states created by hole doping move to the Fermi level. The change in the electronic states is discussed.
- Received 8 November 1993
DOI:https://doi.org/10.1103/PhysRevB.49.13119
©1994 American Physical Society