Photoemission study of the surface electronic structure of Bi-Ca-Sr-Cu-O superconductors modified by Ne sputtering, Ag deposition, and heat treatment

Photoelectron spectroscopy has been utilized to study the effect on the electronic structure of the Bi-Ca-Sr-Cu-O surface of Ne sputtering, deposition of Ag, and annealing in ultrahigh vacuum, aiming at gaining insight into the role of different processing parameters. The results show that all these treatments significantly reduce the valency of Cu in the superconductor, and strongly modify the electronic states in the valence band. In addition, Ne sputtering or annealing in ultrahigh vacuum gives rise to new features in both the O 1s core-level data and in the valence band. We conclude that the electronic structure of the Bi-Ca-Sr-Cu-O surface is very sensitive to different methods of preparation.