PHOTOEMISSION-STUDY OF THE BI2CASR2CU2O8 SUPERCONDUCTOR WITH CU, AG AND AU OVERLAYERS

In this paper, we present a photoemission study of the interaction of Cu, Ag and Au with clean single-crystal Bi2CaSr2Cu2O8 superconductor s urfaces. Both the valence-band and the Bi 5d, O 1 s and Sr 3d core lev els were monitored for all overlayers. Cu, Ag and Au were deposited as consecutively thicker layers starting with a third of a monolayer and progressing in steps up to a deposition in the range of eight monolay ers. Comparing the results for the different overlayers reveals the Ag overlayer to be less reactive than Au which causes the formation of m etallic Bi on cleaved Bi2CaSr2Cu2O8 surface. Cu is shown to be the mos t reactive of the three metals. The Au and Ag overlayers display an is land-growth mode, while Cu grows in a layer-by-layer fashion.