EFFECTS OF PB DOPING ON THE RAMAN-SPECTRUM OF BI2SR2CUO6+DELTA

Partially replacing bismuth by lead in the high-T(c) superconductor Bi 2Sr2CuO6+delta is known to induce an orthorhombic lattice distortion a nd to suppress the incommensurate structural modulation. The Raman spe ctra of Bi2.1-xPbxSr1.9CuO6+delta for a series of samples with 0 less- than-or-equal-to x less-than-or-equal-to 0. 5 have been studied at roo m temperature. The data yield evidence in support of the assignment of the various peaks to vibrational modes of the lattice. A lead-induced vibrational peak at 520 cm-1, which emerges in the more heavily doped samples, is attributed to the vibration of oxygen in 0(2) sites bonde d to lead. In the modulated phase, doubling of the peaks of the unmodu lated structure is observed.