Effect of Y doping on the Bi-O layers of Bi2Sr2CaCu2O8+delta single crystals: a scanning tunnelling microscopy study

Scanning tunnelling microscopy measurements were performed in ultrahigh vac uum on the cleaved (001) surfaces of Bi2Sr2CaCu2O8+delta samples in which 0 , 30 and 46% of the Ca2+ was substituted by Y3+. The structural modulation of the Bi-O planes along [010] was observed on all of the samples, and the average period was measured over a number of images for each sample. The me asured periods were 27.1 +/- 3 Angstrom for 0% Y, 27.7 +/- 3 Angstrom for 3 0% Y, and 25.7 +/- 2 Angstrom for 46% Y. Atomic-resolution images of the 46 % Y-doped sample revealed significant distortions in both the modulation an d the underlying lattice. (C) 1999 Elsevier Science B.V. All rights reserve d.