Intracell changes in epitaxially strained YBa_(2)Cu_(3)O_(7-x) ultrathin layers in YBa_(2)Cu_(3)O_(7-x)/PrBa_(2)Cu_(3)O_(7) superlattices

Abstract

The structure of high quality [YBCO_(N)/PBCO_(M)]_(1000 Å) superlattices, with N ranging between 1 and 12 unit cells and M = 5 unit cells, grown by high oxygen pressure sputtering, is analyzed. Intracell atomic structure of the layers along the c axis and disorder at interfaces is investigated using an x-ray refinement technique. Negligible roughness, step disorder, and interdiffusion are found at the interfaces. Epitaxial mismatch strain results in a surprising reorganization of interatomic distances for the thinnest YBCO layers, which seems to correlated with the decrease in the critical temperature. Intracell structure is invoked as an additional source of T_(c) changes in very thin YBCO layers.