Effect of Iodine Doping on Bi2Sr2Ca1Cu2Ox - Charge-Transfer or Interlayer Coupling

A comparative study has been made of iodine-intercalated Bi2Sr2Ca1Cu2Ox single crystal and 1 atm O2 annealed Bi2Sr2Ca1Cu1Ox single crystal using an AC susceptibility measurement, X-ray photoemission (XPS) and angle-resolved ultraviolet photoemission spectroscopy (ARUPS). The AC susceptibility measurement indicates that O2 doped samples studied have a T(c) of 84 K, whereas T(c) of the iodine-doped samples studied are 80 K. XPS Cu 2p core-level data establish that the hole concentration in the CuO2 planes is essentially the same for these two kinds of samples. ARUPS measurements show that the electronic structure of the normal states near the Fermi level has been strongly affected by iodine intercalation. We conclude that the dominant effect of iodine doping is to alter the interlayer coupling.