Method of producing a high T.sub.c superconducting film free of second phase defects
AssigneeVarian Associates, Inc.
InventorsJames N. Eckstein, Ivan Bozovic
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Abstract
A thin film which is substantially free of measurable surface defects due to second-phase inclusions is disclosed. The film is composed of multilayered strata of a first metal oxide interspersed with single molecular layers of a second metal oxide, where the second metal oxide is effective to absorb second-phase defects which form in the first oxide layers.
Claims13
In the production of a thin film having selected magnetic or conductive properties, by deposition of successive molecular layers of a first high T.sub.c metal oxide which has a relatively narrow temperature-pressure-stoichimetry phase acceptance window, such that second-phase imperfections form during successive layer deposition, the improvement method comprising
- interspersing among said layers at multilayer intervals, a molecular layer of a second metal oxide which has a wider temperature-pressure-stoichiometry phase acceptance window than said first metal oxide, whereby the second-metal oxide layer absorbs the second-phase imperfections formed in the first metal-oxide layers;
- said interspersing preserving the selected magnetic or conduction properties of said thin film while preventing nucleation of second-phase imperfections in the film wherein the ratio of the number of layers of said first high T.sub.c metal oxide to said layer of second metal oxide is R, where R.gtoreq.3;
- where said first high T.sub.c metal oxide layers are selected from a family of cuprate oxide polytype metal oxides including
- (i) M.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7 where M.sub.1 is Y, Nd, La, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, or Lu;
- (ii) Bi.sub.2 Sr.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+4 where n=2 to 5;
- (iii) Tl.sub.x Ba.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+2x+2 where x=1 or 2 and n=1 to 5 or
- (iv) La.sub.2-x (Sr, Ca, Ba).sub.x CuO.sub.4 where x=0 to 0.3;
- and wherein said second metal oxide is selected from the same polytype family as the first metal oxide and wherein said second metal oxide has simpler stoichiometry than said first metal oxide.
A method of producing a high-T.sub.c superconducting thin film which is substantially free of measurable defects due to second-phase inclusions, comprising
- depositing a multilayered stratum composed of molecular layers of a high-T.sub.c polytype metal oxide (HTC) characterized by a relatively narrow temperature-pressure-stoichimetry phase acceptance window, such that second-phase imperfections form during successive layer deposition,
- forming over said stratum by deposition, a molecular layer of a low-T.sub.c metal oxide (LTC) which has a wider temperature-pressure-stoichiometry phase acceptance window than said high Tc metal oxide, whereby the low-T.sub.c molecular layer absorbs the second-phase imperfections formed in said stratum, and
- repeating said depositing and forming steps until a desired number of strata interspersed with said single atomic layers are formed, where the ratio of HTC layers to LTC layers is R and where R.gtoreq.3, where said first high-T.sub.c polytype metal oxide layers are selected from a family of cuprate oxide polytype metal oxides including
- (i) M.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7 where M.sub.1 is Y, Nd, La, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb or Lu;
- (ii) Bi.sub.2 Sr.sub.2 Ca.sub.n-1 Eu.sub.n O.sub.2n+4 where n=2 to 5;
- (iii) Tl.sub.x Ba.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+2x+2 where X=1 or 2, and n=1 to 5 or
- (iv) La.sub.2-x (Sr, Ca, Ba).sub.x CuO.sub.4 where X=0 to 0.3;
- and wherein said second metal oxide is selected from the same polytype family as the first metal oxide and wherein said second metal oxide has simpler stoichiometry than said first metal oxide.
Dependencies are inferred from the claim text.