Growth of stacked heterostructures of SIS-type with S = YBCO orBSCCO and I = (Ba,Ca)CuO2 or (Sr,Ca)CuO2

Abstract

We investigated MOCVD growth ofc-axis two-layer and three-layer stacked heterostructures on(100)SrTiO3 of SI, IS or SIS type. S denotes high temperature superconductor thin films ofYBa2Cu3O7 (Y-123),Bi2Sr2Ca2Cu3O10 (Bi-2223)or Bi2Sr2CaCu2O8 (Bi-2212), while I stands for insulating thin films of(Ba,Ca)CuO2 or(Sr,Ca)CuO2. X-ray diffraction, atomic force microscopy and measurements of resistivity versustemperature were performed after the deposition of each layer. The best results,suitable for further device fabrication, were obtained for the SIS structure(100)SrTiO3/Bi- 2223/(Sr,Ca)CuO2/Bi- 2212. Similarstructures with I = (Ba,Ca)CuO2 have shown higher impurity phases and lower superconducting quality of the topsuperconducting layer. For two-layer or three-layer structures, Bi-2223 as a top layercould not be obtained and, instead, a phase with Bi-2212 formed. Structures with(100)SrTiO3/Y- 123/(Sr,Ca)CuO2/Y- 123 or(100)SrTiO3/Y- 123/(Ba,Ca)CuO2/Y- 123 were also promising, but a current leak often occurred due to greater roughness. Structureswith Y-123 are less sensitive to growth temperature than those with BSCCO.