Materials Letters 15 ( 1993) 338-342 North-Holland Processing of thin films of the three-layer superconducting phase in the Pb-doped Bi-Sr-Ca-Cu-0 system by metalorganic deposition Steve J. Golden ‘, Tamara E. Bloomer, David R. Clarke, Fred F. Lange and Kaushik J. Vaidya Materials Department, College of Engineering, University of California, Santa Barbara, CA 93106, USA Received 20 October 1992 Thin films of the three-layer phase in the Pb-doped Bi-Sr-Ca-Cu-0 system have been processed from metalorganic precursors by spin pyrolysis. The cation composition of the three-layer phase was found to differ significantly from the stoichiometric “2-2- 2-3” composition. Superconductive measurements suggest a distribution of distinct regions with different r, within a pure three- layer thin film. Tem~rature-time-transformation studies were carried out on the three-layer phase in air showing the narrow tem~rature range of stability. It has been found that the one- and two-layer su- perconducting phases in the Bi-Sr-Ca-Cu-0 system exhibit extensive solid solution and contain a sig- nificant number of cation vacancies [ 1,2]. These discoveries have enabled the recent deposition of high-quality, epitaxial thin films of the two-layer phase with high j, on perovskite single-crystal sub- strates [ 31. The superconducting three-layer phase is of particular interest owing to its high T,( > 100 K). However, in contrast to the one- and two-layer phases, the formation of the three-layer phase at high temperature is reported as being extremely sluggish. Various strategies have been used to reduce the re- quired reaction time. Pb-doping has been used to ac- celerate the formation of the three-layer phase but typical heat treatment times for reasonably high yields of three-layer phase are still of the order of 50- 100 h [ 4-6 1. There have been only a limited number of studies characterizing the actual chemical com- position of the three-layer phase [7-lo]. We describe here the rapid fabrication of single- phase three-layer thin films utilizing our knowledge of the solid solution ranges of the one- and two-layer ’ Present address: Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Qfd 4072, Australia. phases. The chemical characterization by calibrated energy-dispersive X-ray microanalysis of the three- layer films processed using metalorganic precursors will be reported. Some preliminary time-tempera- ture-transformation data for the three-layer phase will be given. Bi, Pb, Sr and Ca 2-ethyl hexanoates (M [ OOCsH, 51,) were obtained commercially and Cu 2-ethyl hexanoate was prepared by the reaction of copper acetate and 2-ethyl hexanoic acid. The cat- ion weight percent in each of the precursors was de- termined by inductively coupled plasma spectros- copy (ICPS). Thermogravimetric analysis of the precursors indicated that evaporation of solvent and decomposition of the metalorganic compounds were complete at 450°C. The precursors of Bi, Pb, Sr, Ca and Cu were mixed to form solutions containing var- ious cation ratios. After the attainment of a suitable viscosity by adding or evaporating solvent (chloro- form ), a drop of the precursor was applied to a pol- ished single crystal, 1 cm’ { 1001 MgO substrate mounted on a photoresist spinner. Spin rates were increased up to 7000 rpm depending on the liquid precursor viscosity. The films were pyrolyzed at 450°C for a minute in air. Uniform films of ap- proximately 1 pm thickness were deposited by using 338 0167-577x/93/$06.00 0 1993 Elsevier Science Publishers B-V. All rights reserved.