Systematic X-ray absorption study of hole doping in BSCCO-phases

X-ray absorption spectroscopy (XAS) on the O 1s threshold was applied to Bi-based, single crystalline high temperature superconductors (HT(c)s), whose hole densities in the CuO2 planes were varied by different methods. XAS gives the intensity of the so-called pre-peak of the O 1s line due to the unoccupied part of the Zhang-Rice (ZR) singlet state. The effects of variation of the number n of CuO2-planes per unit cell (n = 1, 2, 3) and the effect of La-substitution for Sr for the to = 1 and 2 phases were studied systematically. Furthermore, the symmetry of the states could be probed by the polarization of the impinging radiation. (C) 2002 Elsevier Science B.V. All rights reserved.