Transport properties of separated pairs of CuO2 planes in (Pb2Cu)Sr2DyxCen-x-δCu2O2n+6 (n=3,5) epitaxial films

The in-plane resistivity and thermopower for Pb-32n2 phase, (Pb2Cu)Sr(2)Ln(x)Ce(n-x-delta)Cu(2)O(2n+6) (Ln=Dy or Eu, n=3 or 5), have been studied. The distance, d, between a pair of CuO2 planes can be arbitrarily chosen in the Pb-32n2 family. So, one can expect the control of electronic anisotropy using this family. The samples were grown by sequential deposition using the molecular beam epitaxy technique. The hole concentration per [CuO], p, was estimated from the thermopower at room temperature. The highest value of p for the Pb-3252 film sample is 0.089, which is within the range for the occurrence of superconductivity in layered cuprates, although resistivity of the Pb-3252 sample shows weak localization behavior. The increase in hole concentration by the substitution of Dy3+ for Ce4+ is lower than expected from the simple calculation of the valence. We discuss possible reasons for these findings and for the absence of superconductivity. The cation deficiency in the fluorite block is supposed to be one of the reasons for the low efficiency of carrier doping and localization behavior. Sheet conductance per CuO2 plane is similar for the Pb-3232 phase (d=0.87 nm) and Pb-3252 phase (d=1.41 nm).