PHOTOELECTRON SPECTROSCOPIC OBSERVATION OF METAL-NONMETAL TRANSITION IN BI2SR2CA1-XYXCU2OY SYSTEM

Photoelectron spectroscopic measurements (XPS and UPS) for single phase polycrystalline Bi2Sr2Ca1−xYxCu2Oy (x=0, 0.5, 0.8 and 1.0 ) were performed. For x=0 sample which is superconducting , a sharp edge at the Fermi energy was observed . As x increased, the intensity of this edge decreased systematically and finally no intensity above background could be observed for x=1.0 sample which is insulating. Tc of this system also decreased as x increased. The results indicate that the observed edge is related to the superconducting properties and the metal-nonmetal transition of this system occurs at 0.5 < x < 1.0, consistent with the results from transport measurements. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.