Single-crystal YBa2Cu3O7−<i>x</i> and Bi2Ca1+<i>x</i>Sr2−<i>x</i>Cu2O8+<i>y</i> surfaces and Ag adatom-induced modification

Abstract

Comparison of x-ray photoemission results for single crystal and polycrystalline YBa2Cu3O7−x allows us to identify oxygen vacancies in the Cu-O chains and determine their effects on the Cu, Ba, and Y core level line shapes. The deposition of adatoms of Ag onto single crystals of YBa2Cu3O7−x and Bi2Ca1+xSr2−xCu2O8+y leads to changes in the Cu 2p3/2 emission indicative of slight Cu2+ to Cu1+ surface reduction, with greater modification for the 1-2-3’s than the 2-1-2-2’s. O 1s core level results show Ag-induced broadening because of these surface effects. The Ba 3d and Y 3d structures showed minimal changes for the 1-2-3 surface. Ag deposition onto the 2-1-2-2 samples also leads to Bi dissociation and subsequent surface segregation.