PHOTOEMISSION AND INVERSE-PHOTOEMISSION STUDY ON BI-2(SR2-XMX)CUOY (M=ND AND GD) OXIDES

Photoemission and inverse-photoemission studies of core-levels, valenc e-bands, and conduction bands of Bi2Sr2-xMxCuOy (M=Nd and Gd) are pres ented. It is found that density of states at the Fermi level is reduce d with increasing trivalent ion contents at Sr sites. Photoemission sp ectra show that energy shifts of core levels and valence and conductio n bands for the samples substituted by Gd, which are non-superconducto rs, are explained by the rigid band model. On the contrary, no energy shift of conduction bands was observed for Bi2Sr2-xNdxCuOy superconduc tors.