The Effect of Yttrium on the Ca and Sr Planes of Y-Doped Bi2sr2ca1cu2o8

Photoemission spectromicroscopy experiments on a series of Y-doped Bi2Sr2Ca1Cu2O8 single crystals show that the doping changes the valence of copper as required for the observed modification of the critical temperature. The doping, however, affects with substitutional reactions not only the CaO planes, but also the SrO planes.