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Scanning Tunneling Microscopy of the Cleaved Surfaces of Bi-Containing Superconductors
Published online by Cambridge University Press: 21 February 2011
Abstract
Scanning tunneling microscopy (STM) images of the cleaved surfaces of Bi2Sr2CaCu2O8 (2212), Bi2Sr2CuO6 (221), and the Pb-substituted Bi1.5Pb0.5Sr2CuO6 (Pb-substituted 221) at room temperature have been obtained. On the 2212 (Tc=85 K) compound, high resolution images show striations ˜10 Å to 30 Å wide. Similar striations of a periodicity of ˜27 Å are also observed on the 221 (Tc=10 K) compound. On the Pb-substituted 221 (Tc=25 K) compound, no periodic structure can be observed. On samples oriented with Laue reflection, the striations are observed to run parallel to the a or b axis of the crystal. These striations are likely to be associated with the undulations along the b axis of the Bi layer observed in recent transmission electron micrographs. For the 2212 compound, comparison of the dependence of scan line characteristics on tunneling bias with calculations on the density of states of each elemental component around the Fermi energy also suggests that tunneling occurs on the Bi face. The topographical and tunneling bias dependence results show that the Bi-rich surfaces of these new superconductors is essentially a termination of the bulk structure even though structural or chemical defects are common.
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- Copyright © Materials Research Society 1989
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