Oxygen Behavior in the Superconductor (Bi,Pb)2Sr2Ca2Cu3Oy Phase Studied by X-Ray Photoelectron Spectroscopy

Abstract

Samples annealed in lower and higher oxygen partial pressure than P(O2) = 10(-2) atm show T(c) shift to the lower temperatures compared with the sample annealed in P(O2) = 10(-2) atm, which shows the highest T(c), 107 K. X-ray Photoelectron Spectroscopy (XPS) measurement was carried out to study the behavior of oxygen and the change of chemical environments of each ion in the high T(c) phase, dependent on the annealing atmosphere changes becoming the origin of these phenomena. The tendency toward increasing binding energies of Bi 4f7/2 and Cu 2p3/2 with increasing oxygen partial pressures during the heat treatments indicates that the mobile oxygens are located in the (Bi, Pb)-O and the Cu-O layers. We know that the valence of Cu moves to +3 with increasing oxygen content in the structure, and this increase of Cu valence indicates the enhancement of hole creation.