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Thin Film Fabrication of High Tc Oxide Superconductors

IP.com Disclosure Number: IPCOM000041043D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chaudhari, P: AUTHOR [+3]

Abstract

Oxide superconductors such as Ba Pb1-x Bix O3 and the tetragon La2-x Mx Cu O4 - (M=Ba,Sr) systems have a very narrow range of compositions in which high superconducting transition tempera- tures occur. Their high Tc's are caused by a strong electron - phonon interaction which is present in only a narrow range of compositions and crystal structure.

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Thin Film Fabrication of High Tc Oxide Superconductors

Oxide superconductors such as Ba Pb1-x Bix O3 and the tetragon La2-x Mx Cu O4 - (M=Ba,Sr) systems have a very narrow range of compositions in which high superconducting transition tempera- tures occur. Their high Tc's are caused by a strong electron - phonon interaction which is present in only a narrow range of compositions and crystal structure.

It is relatively easy to form the proper metals ratio by either sputtering or evaporation techniques. However, subsequent annealing in oxygen does not assure complete oxidation since the kinetics are dominated by the free energy of oxide formation of the metals and the diffusion of oxygen. Metals such as La oxidize preferentially, forming metalloid instead of an oxide. Metals with low vapor pressures such as Sr can be lost during the anneal. Furthermore, the optimum anneal for oxide composition does not necessarily result in the right crystal structure.

It is therefore advantageous to form a film that is close to the desired composition by adding more oxygen during the deposi- tion step. This can be done for the La-Ba-Cu-O system by pre- paring a segmented target having a mixture of oxides and metal pellets sitting on a copper plate. The Ba is fully oxidized as BaO from the decomposition of BaCO3 . La2O3 powder is mixed with this and then pressed into pellets. These are placed on a Cu plate with enough La pellets to give the desired composition, assuming the oxidati...