Growth, structural and electrical characterization of [(Ca,Sr)CuO2]m/[BaCuO2]n superlattices

In this paper we show that (CaCuO2)(m)/(BaCuO2)(n) and (SrCuO2)(m)/(BaCuO2)(n) superlattices with good crystallographic quality can be engineered by Pulsed Laser Deposition (PLD) in a wide range of composition, namely for n = 2 and m = 1-6. However, Sr- and Ca-based superlattices result to have qualitatively different electrical transport properties. Superconductivity is observed in Ca-containing superlattices only. This effect is explained by the large Ba double left right arrow Sr interdiffusion. The resistivity behaviour of the Ca-containing superlattices grown at high oxygen pressure (greater than or equal to 0.2 mbar) is metallic with a full transition to a superconductive state at temperatures as high as 70 K (zero resistance temperature). Such value of T-c, the highest till now reported for an artificial structure, is still lower than those of the related CuBa2Can-1CunOx compounds (T-c = 116 K) obtained by high pressure synthesis. Such difference can be due either to a still unoptimized growth procedure or to the intrinsically higher disorder typical of these artificial structures. (C) 1998 Elsevier Science B.V. All rights reserved.