The invention relates to fabrication of thin film oxide superconductors.
Metal organic deposition (MOD) is a method for fabrication of uniform thickness thin films from liquid precursor solutions as described by Y. L. Chen et al., J. Mater. Res., 4, 1065 (1989). Commonly, metal carboxylates dissolved in organic solvents are deposited on polished substrates by dipping or spin coating with a photoresist spinner. The green precursor films produced by this coating process are transformed into superconductor films by selective heat treatment which often involves multiple distinct calcination steps. Metal organic deposition techniques can be used to deposit films of uniform and controlled composition rapidly and without a need for sophisticated vacuum systems, J. V. Mantese et al., MRS Bull., 14, 48 (1989).
Several investigators have reported preparation of Ba.sub.2 YCu.sub.3 O.sub.7-x (BYC) thin films using metal organic deposition including, Y-M. Chiang et al., Mat. Res. Soc. Symp. Proc., 99, 307 (1988); M. E. Gross et al., Appl. Phys. Lett., 52, 160 (1988); T. Kumagai et al., Chem. Lett., 1645 (1987); M. Klee et al., J. Crys. Growth, 91, 346, (1988). However, these workers observe that the electrical transport properties of metal organic deposited BYC films prepared from metal carboxylate precursors are generally inferior to sputtered, coevaporated and laser ablated films such as those prepared by R. L. Burton et al., submitted to SERI conference, Colorado Springs, Colo., November, 1988; S-W. Chan et al., J. Appl. Phys., 65, 4720 (1989); and P. M. Mankiewich et al., Appl. Phys. Lett., 51, 1753 (1987). Residual precursor materials trapped in MOD films may be responsible for these inferior properties; however, the high processing temperatures needed to completely eliminate precursor residues can cause undesirable reactions between the superconductor film and substrate.