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US 5,231,074 AGranted
Preparation of highly textured oxide superconducting films from MOD precursor solutions
AssigneeMassachusetts Institute of Technology
InventorsMichael J. Cima, Paul McIntyre
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Abstract
Highly-textured superconductor oxide thin films are prepared on substrates, including lattice matched, non-lattice mat The Government has rights in this invention pursuant to contract Number MDA972-88-K0006 awarded by the U.S. Defense Advance Research Project Agency.
Claims29
A method for fabricating a textured superconducting oxide film comprising:
- preparing a metal-organic precursor solution containing cation constituents of the film in a stoichiometry nearly equal to the stoichiometry of the oxide film;
- selecting a substrate that is chemically non-inert with respect to the desired superconducting oxide;
- applying a coating of the precursor solution to said substrate;
- exposing the coating to a heat treatment comprising:
- a first heating at a first temperature in a first controlled atmosphere selected to decompose the precursor coating while avoiding the volatilization of a metal containing precursor constituent;
- a second heating at a second temperature in a second controlled atmosphere selected to create local compositional inhomogeneities in the coating;
- a third heating at a third temperature in a third controlled atmosphere selected to minimize the amount of transient liquid present and to form a compositionally homogeneous film;
- and
- a final heat treatment at a temperature in the range of 400.degree. C. to 500.degree. C. and in an oxygen atmosphere selected to insure that the film is fully oxygenated, thereby producing a textured superconducting oxide phase.
6 more elements
A method for fabricating a textured Ba.sub.2 YCu.sub.3 O.sub.7-x superconductor film on a (100) SrTiO.sub.3 substrate comprising:
- mixing a metal trifluoroacetate precursor solution from powders of BaCO.sub.3, YCO.sub.3 -3H.sub.2 O and Cu(OH).sub.2 CO.sub.3 in an approximately 2:1:3 ratio and reacting them with between 20% and 30%, 5.5-6.0M excess trifluoroacetic acid in methyl alcohol, followed by refluxing for approximately four hours to produce a solution substantially 0.94M based on copper content;
- applying a coating of the precursor solution to a polished (100) SrTiO.sub.3 substrate with photoresist spinner at a speed in the range of approximately 3000-5000 rpm depending on substrate dimensions;
- heating the coating slowly, at a rate approximately in the range of 0.5.degree.-1.0.degree. C./min, in moist oxygen having a dew point approximately in the range of 20.degree.-75.degree. C. to a temperature approximately in the range 300.degree.-500.degree. C. to decompose the metal-containing precursor;
- heating the coating for approximately one hour in moist reducing nitrogen/oxygen gas mixture, having a composition approximately in the range of 0.1-5% O.sub.2 at a temperature below 810.degree. C. so as to create local inhomogeneities in the film and to minimize the amount of transient liquid present;
- and
- cooling the coating from said temperature range in dry oxygen with a hold for a time in excess of 2 hours at temperatures approximately in the range 400.degree.-500.degree. C. to fully oxygenate the film such that a textured superconducting oxide film is obtained.
3 more elements
A method for fabricating a textured Ba.sub.2 YCu.sub.3 O.sub.7-x superconductor film on a BaZrO.sub.3 substrate comprising:
- mixing a metal trifluoroacetate precursor solution from powders of BaCO.sub.3, YCO.sub.3 -3H.sub.2 O and Cu(OH).sub.2 CO.sub.2 in an approximately 2:1:3 ratio and reacting them with 5.5-6.0M excess trifluoroacetic acid in methyl alcohol, followed by refluxing for approximately ten hours to produce a viscous solution;
- applying a coating of the precursor to a polished BaZrO.sub.3 substrate with a photoresist spinner at a speed approximately in the range of 3000-7500 rpm depending on substrate dimensions;
- heating the coating slowly, at a rate approximately in the range of 0.5.degree.-1.0.degree. C./min, in moist oxygen or nitrogen to a temperature in the range of 300.degree.-500.degree. C. to decompose the metal-containing precursor;
- heating the coating for a time approximately in the range of 0.25-4.00 hour in moist oxygen or nitrogen at a temperature approximately in the range of 650.degree.-850.degree. C. to create local compositional inhomogeneities in the coating;
- heating the coating at a rate approximately in the range of 5.degree.-20.degree. C./min to a temperature approximately in the range of 860.degree.-950.degree. C. for a time approximately in the range of 5-30 minutes to form a small amount of transient liquid;
- cooling the coating from said temperature range in flowing dry oxygen to a temperature approximately in the range of 400.degree.-500.degree. C. to fully oxygenate the film;
- and
- further cooling the coating to room temperature in static dry oxygen such that a textured superconducting film is obtained.
5 more elements
A method for fabricating a textured superconducting oxide film comprising:
- preparing a metalorganic precursor solution containing cation constituents of the film in a stoichiometry nearly equal to the stoichiometry of the oxide film;
- selecting a substrate that is chemically inert with respect to the desired superconducting oxide with a transient liquid phase;
- applying a coating of the precursor solution to said substrate;
- exposing the coating to a heat treatment comprising:
- at first heating at a first temperature in a first controlled atmosphere selected to decompose the precursor coating while avoiding the volatilization of a metal containing precursor constituent;
- a second heating at a second temperature in a second controlled atmosphere selected to create local compositional inhomogeneities in the coating;
- a third heating at a third temperature in a third controlled atmosphere selected to form a small amount of transient liquid sufficient to increasing the rate of grain growth and to form a compositionally homogeneous film;
- and
- a final heat treatment at a atmosphere in the range of 400.degree. C. to 500.degree. C. to insure that the film is fully oxygenated, thereby producing a textured superconducting oxide phase.
6 more elements
Dependencies are inferred from the claim text.