BI2-XCUOY ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.40) STUDIED BY PHOTOEMISSION AND INVERSE-PHOTOEMISSION SPECTROSCOPY(XSR2)

Bi2+xSr2-xCuOy (0.10 less-than-or-equal-to x less-than-or-equal-to 0.4 0) polycrystalline samples have been studied by x-ray diffraction, res istivity and Hall-coefficient measurements, x-ray and ultraviolet phot oemission spectroscopy, and inverse-photoemission spectroscopy (IPES). The lattice constant of the c axis decreases and that of the a (b) ax is increases as a function of x. The results of Hall-coefficient measu rements indicate that hole concentration is reduced as a function of x , which is consistent with the results of oxygen-concentration measure ments. 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 Bi2Sr2Ca1-xYxCu2Oy 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 t he Fermi level. The change in the electronic states is discussed.