Metal-organic chemical vapor deposition as an emerging technique for the fabrication of YBa2Cu3Ox tapes

The deposition of YBa2Cu3Ox thin films on metal substrates is currently being investigated as the basis for future tape applications. The YBa2Cu3Ox coatings, discussed in this report, are deposited by metal-organic chemical vapor deposition (MOCVD). MOCVD is a versatile technique with many opportunities in terms of reaction chamber design and shapes of substrates to be coated. MOCVD equipment for fabrication of YBa2Cu3Ox coatings on long length, flexible metal tapes is currently being developed. Tapes of various materials, such as polycrystalline stainless steel, have been investigated. The growth of biaxially aligned buffer layers between the stainless-steel tapes and YBa2Cu3Ox coatings is necessary, to prevent interdiffusion, to reduce interfacial reactions and to allow the succeeding growth of aligned YBa2Cu3Ox thin films. The superconducting properties of the resulting YBa2Cu3Ox/buffer/substrate thin film systems, T(c)approximate to 90 K and J(c)>10(5) A cm(-2), are very promising, the major drawbacks in MOCVD of YBa2Cu3Ox thin films are the thermo-chemical properties of MOCVD precursors. For example, the traditional solid precursors have limited volatility. The development of new precursor delivery systems using precursor solutions and new solid and liquid precursors have resulted in improved process reliability. Finally, in the standard MOCVD process, which is thermally activated, the reported growth rates are approximately 0.5 mum h(-1). An increase by one order of magnitude can be achieved in a photo-assisted MOCVD process. (C) 1998 Elsevier Science Ltd. All rights reserved.