PHOTOELECTRON SPECTROSCOPIC STUDY OF BA1-XRBXBIO3

A photoelectron spectroscopic study to investigate the electronic structure of a noncuprate oxide superconductor Ba(1-x)Rb(x)BiO3 (0 less-than-or-equal-to x less-than-or-equal-to 0.4) system is reported. Comparison of the results with those inconclusively reported for Ba(1-x)K(x)BiO3 and BaPb(1-x)Bi(x)O3 is discussed. It is concluded that the chemical environment of substituted Rb in this system is similar to that of Rb metal, corelevel binding energies of Bi and Ba are unaffected by Rb substitution, and the shift of the valence band towards lower binding energy upon hole-carrier doping is observed. A characteristic change of the density of states in the vicinity of the Fermi level with composition x is observed, suggesting that the nonmetal-to-metal transition occurs through a continuous change of the electronic states of the system.