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Science 8 June 1990:
Vol. 248. no. 4960, pp. 1211 - 1214
DOI: 10.1126/science.248.4960.1211
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Articles

Structural and Electronic Role of Lead in (PbBi)2Sr2CaCu2O8 Superconductors by STM

Xian Liang Wu 1, Zhe Zhang 1, Yue Li Wang 1, and Charles M. Lieber 1

1 Department of Chemistry, Columbia University, New York, NY 10027

The structural and electronic effects of lead substitution in the high-temperature superconducting materials PbxBi2-xSr2CaCu2O8 have been characterized by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Large-area STM images of the Bi(Pb)—O layers show that lead substitution distorts and disorders the one-dimensional superlattice found in these materials. Atomic-resolution images indicate that extra oxygen atoms are present in the Bi(Pb)—O layers. STS data show that the electronic structure of the Bi(Pb)—O layers is insensitive to lead substitution within ±0.5 electron volt of the Fermi level; however, a systematic decrease in the density of states is observed at ap1 electron volt above the Fermi level. Because the superconducting transition temperatures are independent of x(Pb) (x le 0.7), these microscopic STM and STS data suggest that the lead-induced electronic and structural changes in the Bi(Pb)—O layer do not perturb the electronic states critical to forming the superconducting state in this system.

Submitted on January 17, 1990
Accepted on March 27, 1990


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