Superconductor structure

A superconductor structure having a substrate, the substrate defining a surface. Applied to the surface of the substrate is a barrier layer. Applied to the barrier layer is a layer of superconductive material comprising copper and oxygen. The barrier layer serves to prevent the interaction of the superconductive material with the substrate, thus destroying the stoichiometry of the superconductive material and resulting in a loss or decrease in superconductivity. A protective layer is, optionally, applied to the layer of superconductive material.

BACKGROUND OF THE INVENTION 
The present invention relates to a superconductor structure. Specifically, 
the present invention relates to a superconductor structure comprising a 
barrier layer of material between a superconductive material and a 
substrate. 
Superconductors refer to a class of compounds which exhibit a complete 
disappearance of electrical resistance and repel the magnetic field from 
the inner volume of the material (Meisner effect) under certain 
conditions. While various superconductors have been known for a number of 
years, practical applications for such superconductors have been limited 
due to a variety of factors. For example, a number of compounds which 
exhibit superconductivity only exhibit such superconductivity at 
temperatures near absolute zero. Due to the difficulty of maintaining such 
low temperatures, the practical applications of such superconductors have 
been severely limited. 
Recently, a massive research effort has been conducted in an attempt to 
identify compositions exhibiting superconductivity which compositions are 
capable of exhibiting superconductivity at temperatures significantly 
above absolute zero. 
One type of compound which has been found to exhibit superconductivity at 
temperatures above absolute zero are certain ceramic compositions 
comprising copper and oxygen, beneficially comprising copper, oxygen and 
at least one element selected from the group consisting of bismuth, 
strontium, calcium, thallium, indium and the rare earth elements and 
particularly compounds having the general formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
wherein Re represents a rare earth element selected from the group 
consisting of Er, Gd, Y, Tm, Sm, Eu, Dy, Ho, Yb, Nd, and Lu and 
0.ltoreq.x.ltoreq.0.5. When x is within the described ranges, the oxygen 
content of the composition is between about 6.5 and 7.0 per unit formula. 
The ceramic compositions represented by the above described formula 
exhibit superconductivity at a temperature between 90-100K. While 90-100K 
is still a very low temperature, maintaining a superconductor at such a 
temperature is greatly simplified when compared to maintaining a 
superconductor at or near absolute zero. For example, a temperature of 
90-100K can be maintained by employing liquid nitrogen as a coolant. Thus, 
the ceramic superconducting compounds described above are attractive 
possibilities in the attempt to adapt superconducting materials for 
practical applications. 
Despite the advantage of demonstrating superconductivity at higher 
temperatures, the ceramic compositions described above suffer from various 
other drawbacks. For example, it is known that in order for the described 
ceramic compositions to exhibit superconductivity, it is important to 
maintain the stoichiometry of the various elements within very specific 
ratios, such as those described by the above formula. If the stoichiometry 
of the compositions is not maintained, the compositions tend to 
deteriorate and eventually lose their superconductivity. 
Additionally, the described ceramic superconductive compositions tend to 
interact with other materials with which they are in contact. Such 
interaction between the ceramic superconductive materials and other 
materials with which they come in contact generally results in the loss of 
stoichiometry in the materials, thus resulting in the decomposition and 
eventual loss of superconductivity. 
For example, it is often desirable to employ a relatively thin layer of 
superconductive material in a device. In those instances wherein it is 
desired to employ a relatively thin layer of superconductive material, it 
is often necessary to use a substrate as a support for the thin layer of 
superconductive material. 
Unfortunately, it has been discovered that when it is desired to apply a 
relatively thin layer of superconductive material to a substrate, 
interaction can occur between the material from which the substrate is 
formed and the layer of superconductive material. As a result of this 
interaction, at least a portion of the layer of superconductive material 
closest to the substrate will lose the stoichiometry desired to impart the 
superconductivity to the superconductive layer. In effect, and as result 
of this intraction, a multi-phase layer is formed. 
Various attempts have been made to avoid or compensate for the interaction 
between the substrate and superconductive material layer. For example, it 
has been suggested that the substrate be selected so that there is a 
minimum amount of interaction between the substrate layer and the layer of 
superconductive material. For example, one of the most common substrates 
employed in the electronics industry is alumina (Al.sub.2 O.sub.3). 
Unfortunately, alumina has been found to be relatively reactive with 
ceramic superconductive materials. Accordingly, it has been proposed that 
strontium titanate (SrTiO.sub.3) be employed as the substrate material. 
This is because SrTiO.sub.3 has been found to be relatively less reactive 
with the ceramic superconductive materials than alumina and allows for the 
epitaxial growth of thin films of superconductive materials according to 
the formula Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x. 
Unfortunately, SrTiO.sub.3 is more expensive and less readily available for 
use as a substrate and is still somewhat reactive with ceramic 
superconductive materials. Additionally, SrTiO.sub.3 has a very high 
dielectric constant which limits its use in high frequency applications. 
Many of the proposed applications for superconductive materials would 
benefit if it were possible to employ the substrates normally employed 
with electronic devices in forming superconductor structures. 
Moreover, ceramic superconductive materials comprising copper and oxygen 
have been found to possess relatively poor adhesion to many substrates. 
For example, when a ceramic superconductive material comprising copper and 
oxygen is applied to an alumina substrate at a relatively low temperature, 
the ceramic superconductive layer will often peel off the substrate. When 
applied at a higher temperature, peeling may be avoided but the higher 
temperature enhances the deleterious interaction between the substrate and 
the superconductive layer. 
SUMMARY OF THE INVENTION 
It is desirable to produce a superconductor structure comprising a 
substrate and a layer of ceramic superconductive material applied to the 
substrate, which superconductive material does not lose its stoichiometry 
due to interaction with the substrate layer and adheres well to the 
substrate. It is to this goal that the present invention is directed. 
In a second aspect, the present invention concerns a method of fabricating 
a superconductor structure which comprises a substrate and a layer of 
ceramic superconductive material applied to the substrate which 
superconductive material is prevented from stoichiometric deterioration 
due to interaction of the superconductive material with the substrate 
material. Moreover, it is desirable to be able to form the substrate layer 
out of substrate materials generally known for use in electronic devices. 
Specifically, it is desirable to be able to employ substrate materials 
which, when allowed to come into direct contact with the superconductive 
material such as those described above, tend to deteriorate the 
stoichiometry of the superconductive materials and tend not to adhere well 
to the superconductive materials. 
These and other related goals are achieved in a superconductor structure 
comprising a substrate which defines a surface. Applied to the surface of 
the substrate is a barrier layer. Applied to the barrier layer is a layer 
of ceramic superconductive material comprising copper and oxygen. The 
barrier layer serves the dual function of preventing or substantially 
reducing the interaction between the substrate material and the layer of 
superconductive material and of increasing the degree of adhesion between 
the substrate material and superconductor material layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In one aspect, the present invention concerns a superconductor structure 
comprising a superconductive material comprising copper and oxygen, 
beneficially comprising copper, oxygen and at least one element selected 
from the group consisting of bismuth, strontium, calcium, thallium, indium 
and the rare earth elements, and preferably being represented by the 
formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
wherein Re represents a rare earth element selected from the group 
consisting of Er, Gd, Y, Tm, Sm, Eu, Dy, Ho, Yb, Nd, and Lu and 
0.ltoreq.x.ltoreq.0.5, and a substrate layer. The superconductive material 
is protected from stoichiometric deterioration due to interaction of the 
superconductive material with the substrate material. 
The superconductor structure of the present invention comprises a substrate 
which defines a surface. Applied to the surface of the substrate is a 
barrier layer and applied to the barrier layer is a layer of a ceramic 
superconductive material comprising copper and oxygen, beneficially 
comprising copper, oxygen and at least one element selected from the group 
consisting of bismuth, strontium, calcium, thallium, indium and the rare 
earth elements, and preferably according to the formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x. 
Referring now to FIG. 1, the structure of the present invention is 
generally represented by the reference numeral 10. The structure comprises 
a substrate 12 defining a surface on which is applied a barrier layer 14 
which in turn has applied thereto a superconductive material layer 16. 
Those skilled in the art will appreciate the wide variety of materials 
suitable for use in forming the substrate of the present invention. As a 
general rule, materials known to be suitable for use in forming, or being 
substrates for semiconductor devices are suitable for use in the present 
invention. Exemplary of materials from which the substrate may be 
fabricated are alumina, sapphire, boron nitride, berrilium oxide, 
magnesium oxide, zirconium oxide, strontium titanate and the like. While a 
relatively wide variety of materials is believed to be suitable for use in 
forming a subtrate of the present invention, for reasons such as cost, 
relative ease of availability, standard process technology associated 
therewith and its extensive use in the semiconductor industry, alumina is 
the desired material from which to form the substrate. 
The substrate generally serves as a support for the ceramic superconductive 
material layer. Accordingly, the thickness of the substrate may be 
selected within a fairly wide range. Generally, the substrate will have a 
thickness of from about 5 mils to about 100 mils, desirably from about 10 
mils to about 40 mils. The substrate may have a multilayer construction 
such as, for example, aluminum oxide coated, via sputtering, on silicon. 
Methods of forming the substrate are well known to those skilled in the 
art. Additionally, while in the illustrated embodiment the substrate is 
depicted as being generally planar in nature, it is to be understood that 
the substrate may be formed into a variety of different shapes and sizes. 
Exemplary of alternative shapes would be wires, spheres and the like. 
Applied to the surface of the substrate is a barrier layer. It is believed 
that the barrier layer of the present invention can be formed from a wide 
variety of materials. The barrier layer serves to prevent or substantially 
reduce the degree of interaction between the superconductive material 
layer and the substrate layer and desirably promotes adhesion between the 
substrate and superconductive material layer. In effect, the barrier layer 
should be capable of good adhesion to the substrate as well as good 
adhesion to the layer of superconductive material. 
It has been found that when a composition comprising copper is employed as 
the ceramic superconductive material and is in direct contact with a 
substrate, the substrate and superconductive material often interact to 
deplete the amount of copper present in the superconductive material. 
Accordingly, the barrier layer desirably comprises copper so that when the 
barrier layer is allowed to contact the substrate, the substrate interacts 
with the copper present in a barrier layer. When the superconductive 
material layer is later applied to the barrier layer, very little 
interaction between the superconductor material and substrate occurs. 
Copper is generally present in a barrier material layer in accordance with 
a preferred embodiment of the present invention in an amount of from about 
20 atomic percent to about 80 atomic percent, preferably from about 40 
atomic percent to about 60 atomic percent based on total weight of barrier 
layer material. 
It is believed that the barrier layer may comprise a number of different 
elements in addition to copper. Any element or compound which functions in 
the described manner is suitable for use in the present invention. 
Exemplary of the elements which may be combined with copper to form the 
barrier layer are oxygen, barium, yttrium, lanthanum and mixtures thereof. 
It has been found that one desirable barrier layer comprises barium and 
copper, preferably barium, copper and oxygen in the form of barium copper 
oxide (BaCuO.sub.2). A barium copper oxide barrier layer has been found to 
be particularly well suited for use with ceramic superconductive materials 
represented by the formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
It is desirable that the barrier layer have a crystal structure similar to 
the crystal structure of the superconductive material layer. This 
similarity in crystal structure is desirable because it tends to lessen 
the interference between the substrate layer and the crystal structure of 
the superconductive material. Superconductive materials represented by the 
formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
generally have an orthorhombic perovskite crystal structure. Accordingly, 
it has been found useful to employ barrier layer materials having a 
perovskite crystal structure since such a structure is similar to a 
orthorhombic crystal structure. The barrier layer comprising barium copper 
oxide has such a crystal structure. Accordingly, other oxides comprising 
copper and possessing a perovskite crystal structure are believed to be 
suitable for use in forming the barrier layers according to the present 
invention. 
The barrier layer material of the present invention may be applied directly 
to the substrate in the barrier layer form or may be formed in a one-step 
process on the substrate from starting materials known to form the barrier 
layer material. For example, when barium copper oxide is employed as the 
barrier layer material, barium copper oxide may be applied directly to the 
substrate or, alternatively, a mixture of copper oxide (CuO) and barium 
carbonate (BaCO.sub.3) may be formed and applied to the substrate. The 
substrate coated with the copper oxide and barium carbonate mixture may 
then be subjected to a heat treatment at a temperature between about 
850.degree. C. and about 1100.degree. C. during which the copper oxide and 
barium carbonate react to form barium copper oxide. 
The barrier layer material is suitably applied to the substrate in the form 
of a paste. The paste is formed by mixing powdered barrier layer material 
(such as BaCuO.sub.2) with a binder material (such as ethyl cellulose) 
dissolved in a solvent (such as 2-(2-butoxyethoxy)ethanol). Similarly, if 
the barrier layer material is to be formed in a one-step process, the 
starting materials (such as CuO and BaCO.sub.3) may be applied to the 
substrate in the form of a paste. The paste is formed from powdered 
starting materials, a binder (such as ethyl cellulose) and a solvent (such 
as 2-(2-butoxyethoxy)ethanol). The paste in either instance may be applied 
to the substrate by painting or by screen printing. 
Regardless of whether the barrier layer material is applied directly to the 
substrate or is formed in a one-step process on the substrate, it is 
preferable that the barrier layer material be subsequently exposed to a 
heat treatment step wherein the barrier layer material is heated above its 
melting point. This causes the barrier material to liquify and flow over 
the surface of the substrate. Since a relatively thin layer of barrier 
material may be employed in the structures of the present invention, it is 
generally desirable that the barrier layer be formed from a material which 
"wets" the surface of the substrate material. By the term "wets", it is 
meant that the surface tension between the surface of the substrate and 
the barrier layer, in a molten state, is very low. This allows for the 
easy formation of a thin layer of barrier layer material. In the case 
where the barrier layer is formed in a one-step process, this heat 
treatment beneficially occurs as part of the process in which, for 
example, BaCO.sub.3 and CuO are converted to BaCuO.sub.2. 
The ratio of barium to copper in the barrier layer comprising barium copper 
oxide may vary from about 1:20 to 1:0.5. The ratio of barium to copper is 
beneficially from about 1:13 to about 1:1. The exact ratios of the various 
elements making up the barrier layer material will vary depending on the 
composition of the substrate material and the interaction between 
substrate and superconductive material layers. 
The barrier layer is preferably thick enough to prevent an undesirable 
degree of interaction between the substrate and the superconductive 
material layer. As a general rule, the thickness of the barrier layer is 
suitably from about 0.1 .mu.m to about 200 .mu.m, beneficially from about 
5 .mu.m to about 80 .mu.m, and preferably from about 10 .mu.m to about 40 
.mu.m. 
The superconductive material used to form layer 16 in FIG. 1 comprises 
copper and oxygen, beneficially copper, oxygen and at least one element 
selected from the group consisting of bismuth, strontium, calcium, 
thallium, indium, and the rare earth elements, and is preferably 
represented by the formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
wherein Re is a rare earth element selected from a group consisting of Er, 
Gd, Y, Tm, Sm, Eu, Dy, Ho, Yd, Nd, and Lu and 0.ltoreq.x.ltoreq.0.5. 
Compositions according to the above described formula are known to those 
skilled in the art. In one embodiment to the present invention, Re is 
selected from the group consisting of Y, Er, and Gd. Methods of 
fabricating the superconductive materials represented by the above 
described formula are known to those skilled in the art. The method by 
which the superconductive material is formed is not believed to be 
critical to the present invention. Accordingly, any method of production 
is suitable to form the superconductive materials for use in the present 
invention. 
The layer 16 of superconductive material suitably has a thickness of from 
about 0.1 .mu.m to about 200 .mu.m. Applicant has found that it is often 
more simple to obtain the proper stoichiometry when the layer of 
superconductive material is relatively thick. As used herein, a layer of 
superconductive material which is relatively thick will generally have a 
thickness of from about 5.0 .mu.m to about 100 .mu.m, preferably from 
about 10 .mu.m to about 80 .mu.m. 
Methods of applying the layer of superconductive material to the substrate 
are known to those skilled in the art. As a general rule, one of two 
methods will be employed. First, it is possible to form a powder of the 
superconductive material having the above described composition. This 
powder is then mixed with a binder to form a resultant paste. The binder 
generally comprises a material capable of binding the particles together, 
said material being dissolved in a solvent. Exemplary of a suitable binder 
is ethyl cellulose in a solvent (such as 2-(2-butoxyethoxy)ethanol). The 
resultant paste is applied to the substrate to a desired thickness. The 
substrate and paste of superconductive material can then be fired at 
temperatures between about 800.degree. C. and about 1100.degree. C. to 
burn off the binder and solvent thus leaving a layer of superconductive 
material. 
Alternatively, applicant has discovered that it is possible to form the 
superconductive material in a onestep process from a paste-like material. 
That is, rather than employ a powder of a superconductive material, it is 
possible to form a paste comprising the oxides and carbonates known to 
form the superconductive materials of the present invention. These oxides 
and carbonates are mixed with a binder (such as ethyl cellulose) and a 
solvent (such as 2-(2-butoxyethoxy)ethanol). The resultant paste-like 
mixture can then be applied to the substrate. The substrate and described 
paste-like mixture are then subjected to a firing process similar to the 
firing process normally employed in forming superconductive materials of 
the formula: 
EQU Re.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x 
In this manner, the binder and solvent are driven off and the 
superconductive layer can be formed in what is essentially a one-step 
process. 
Nonetheless, while forming the superconductive material in a one-step 
process may represent some economic advantages, it is not believed 
critical to the present invention. Moreover, any thin or thick film 
deposition methodology, as well as bulk technology, is believed to be 
appropriate for use in the current invention. For example, the 
superconductive material layer may be formed by molecular beam epitaxy, 
sputtering, reactive evaporations and the like. When such methods are 
used, relatively thin layers are generally formed (0.2 .mu.m-2.0 .mu.m). 
The superconductive materials described above are known to be capable of 
interaction with water, water vapor, carbon dioxide and the like. 
Accordingly, while the barrier layer described above prevents interaction 
between the substrate and the superconductive material layer, it is 
possible for the superconductive materials to lose their stoichiometry due 
to interaction of the superconductive materials with water, air, water 
vapor, carbon dioxide and the like. Accordingly, it is desirable to 
protect the superconductive materials from exposure to water, air, water 
vapor, carbon dioxide and the like. A method suitable for protecting the 
superconductive materials from loss of stoichiometry due to exposure to 
water, air, water vapor, carbon dioxide and the like is disclosed in 
co-pending U.S. patent application Ser. No. 07/544,021, filed Jun. 25, 
1990, which is a file wrapper continuation of Ser. No. 198,735, filed Jun. 
9, 1988 (on even date with this application) now abandoned for 
SUPERCONDUCTOR STRUCTURE by Meir Bartur which application is incorporated 
herein by reference. As set forth in the referenced U.S. patent 
application, it is possible to form a protective layer on the 
superconductive material. The protective layer is intended to protect the 
superconductive material from exposure to water, air, water vapor, carbon 
dioxide and the like and thus prevent loss of stoichiometry and the 
resultant loss of superconductivity. 
Any material capable of performing the above functions and of being applied 
to the superconductive material and which is compatible with said 
superconductive material (producing no loss of stoichiometry or otherwise 
deliteriously affecting the superconductive material) is suitable for use 
in the present invention. Exemplary of the materials from which the 
protective material layer may be formed are silicon dioxide (SiO.sub.2) 
and silicon nitride (Si.sub.3 N.sub.4). These materials are preferred due 
to the ready availability of deposition methodology and equipment for 
their use, ease of deposition, ability to perform the described function 
and relative inertness to the superconductive materials at low 
temperatures. 
A variety of methods are suitable for use in applying the protective layer 
to the superconductive material. However, elevating the superconductive 
materials to temperatures in excess of about 250.degree. C. can result in 
the evolution of oxygen by the superconductive material and the resultant 
loss or decrease in superconductivity. Accordingly, it is desirable to 
employ a method which does not deliteriously affect the superconductive 
material layer. 
Exemplary of the methods suitable for use in applying the protective layer 
to the superconductive material is the low pressure, plasma enhanced 
chemical vapor deposition process (LPPECVD). Those skilled in the art will 
recognize what is meant by a low pressure, plasma enhanced chemical vapor 
deposition process. Such a process is desirable for use in the present 
invention because it allows the protective material layer to be applied at 
relatively low temperatures, typically in the range of from about 
20.degree. C. to about 450.degree. C. Additionally, the LPPECVD process 
causes ions having a relatively low energy level to impinge upon the 
surface of the superconductive material layer. Thus, the interaction and 
loss of stoichiometry in the superconductive material is less likely to 
occur when the LPPECVD process is employed. 
It is believed that a relatively thin layer of the protective material will 
prevent loss of stoichiometry during subsequent deposition of additional 
protective layer material. Therefore, it may be possible to employ an 
LPPECVD method in conjunction with a different method, such as RF 
sputtering to form the layer of protective material. In such an instance, 
the initial thickness of protective layer material would be applied 
through a LPPECVD process with additional amounts of the protective layer 
material being applied through an RF sputtering process. Typically, the 
layer of protective material will have a thickness capable of performing 
the above described protective function. Generally, the layer of 
protective material will have a thickness of from about 100 Angstroms to 
about 26 .mu.m, beneficially from about 1000 Angstroms to about 10 .mu.m 
and preferably from about 1000 Angstroms to about 10,000 Angstroms. The 
exact thickness of the protective layer of material will depend, to an 
extent, on the material from which the protective layer is formed, the 
roughness of the superconductive material and the environment in which the 
device of the present invention is to be used. 
FIG. 2 illustrates a cross-section of a second embodiment of the present 
invention. The structure of the present invention is generally represented 
by the numeral 18. The structure 18 comprises substrate 20, barrier layer 
22, superconductive material layer 24, and protective layer 26. In this 
embodiment of the present invention, the superconductive material is 
prevented from loss of stoichiometry by both interaction of the 
superconductive material with the substrate or by interaction of the 
superconductive material with water, air, water vapor, carbon dioxide and 
the like. 
It is anticipated that in certain applications wherein the substrate is 
particularly reactive towards the layer of superconductive material, that 
it may be desirable to employ a second diffusion barrier layer between the 
substrate and the layer of ceramic superconductive material. For example, 
in known semiconductor technology, when silicon is employed as a 
substrate, it is known to employ a diffusion barrier such as TiW, W, WN, 
TiN, or Cr. These diffusion barriers would aid in preventing the diffusion 
of copper out of the layer of superconductive material. In those 
instances, when a further diffusion barrier is desired, the diffusion 
barrier would be evaporated onto the substrate according to known 
technology to a thickness of from about 500 Angstroms to about 2000 
Angstroms. The barrier layer material would then be applied to the first 
diffusion barrier as herein before described. Similarly, the layer of 
ceramic superconductor material and, optionally, the protective material 
layer would be applied as hereinbefore described. 
EXAMPLES 
Example 1 
A structure according to the present invention is formed in the following 
manner. 
A substrate of alumina (96% density) is provided. The substrate is in the 
form of a rectangle one inch by two inches having a thickness of 
approximately 20 mils. 
The material from which a barrier material layer is to be formed is 
prepared as follows. 
A fine powder of copper oxide (CuO) and barium carbonate (BaCO.sub.3) is 
prepared by grinding. The powders are mixed in appropriate ratios to form 
a resultant powder mixture wherein the Ba:Cu atomic ratio is within the 
range of from about 1:13 to about 1:0.4. To the resultant powder mixture 
is then added about 15 to about 40 weight percent, based on total mixture 
weight, a binder comprising ethyl cellulose and 2-(2-butoxyethoxy)ethanol 
(6 g/100 cc) to form a paste. 
The paste is then applied to one side of the substrate via painting to a 
thickness of about 60 .mu.m. The substrate is then dried by heating to 
about 125.degree.-150.degree. C. to drive off the 
2-(2-butoxyethoxy)ethanol. Following the drying process, the substrate is 
subjected to a heat treatment. 
The heat treatment is conducted in an open quartz tube furnace, four inches 
in diameter. The quartz tube furnace is held at a temperature of about 
525.degree. C. in a flowing oxygen atmosphere. After about 20 minutes, the 
temperature is gradually ramped up to between 750.degree. C. and 
1100.degree. C. for approximately two hours. The substrate is then slowly 
cooled to room temperature. 
The material from which a superconductive material layer is to be formed is 
prepared as follows. 
An intimate admixture of Y.sub.2 O.sub.3, BaCO.sub.3 and CuO appropriate to 
form a composition according to the unit formula Y.sub.1 Ba.sub.2 Cu.sub.3 
O.sub.7-x is formed. The mixture is suitably formed by mixing and grinding 
in a ball mill or mortar and pestle. To the mixture is then added about 15 
to about 40 weight percent, based on total mixture weight, of a binder 
comprising ethyl cellulose and 2-(2-butoxyethoxy)ethanol (6 g/100 cc) to 
form a paste. 
The paste is then applied to the barrier layer via painting to a thickness 
of about 80 .mu.m. The structure is then dried by heating to about 
125.degree.-150.degree. C. to drive off the 2-(2-butoxyethoxy)ethanol. 
Following the drying process, the coated substrate is loaded into an open 
quartz tube furnace held at a temperature of about 525.degree. C. in an 
O.sub.2 and N.sub.2 (10/5) atmosphere. After about 20 minutes, the 
temperature is gradually ramped up to between 875.degree. C. and 
975.degree. C. The substrate is held at this temperature for 2-20 hours. 
Then, the substrate is slowly cooled to about 500.degree. C. and held in 
an O.sub.2 atmosphere for 1-24 hours. The substrate is then slowly cooled 
to room temperature. 
In this manner, a structure such as that illustrated in FIG. 1 is produced. 
Example 2 
A structure according to FIG. 2 of the instant invention is produced in the 
following manner. 
The structure as described in Example 1 comprising a substrate, a barrier 
layer, and a superconductive material layer is formed as set forth in 
Example 1. To the structure of Example 1 is then applied a protective 
material layer in the following manner. 
The structure of Example 1 is placed in a standard low pressure plasma 
enhanced chemical vapor deposition chamber. The substrate is held at room 
temperature. The deposition chamber is evacuated over a period of about 
1-3 minutes to about 100-300 .mu. torr. A gas mixture of SiH.sub.4 and 
NO.sub.2 or NH.sub.3 (1:1-40:1) is fed into the deposition chamber. The 
pressure in the chamber is controlled at about 150-800 .mu. torr. RF power 
is applied for about 1-30 minutes. When a mixture of SiH.sub.4 and 
NO.sub.2 is employed, SiO.sub.2 is deposited. When a mixture of SiH.sub.4 
and NH.sub.3 is employed, Si.sub.3 N.sub.4 is deposited. The deposited 
layer will have a thickness of from about 500 to about 10,000 Angstroms 
depending on deposition time. 
As is apparent from the foregoing specification, including the examples, 
the present invention is capable of being embodied with various 
alterations and modifications from those described above. For this reason, 
it is to be fully understood that all of the foregoing is intended to be 
merely illustrative and is not intended to limit, in any manner, the scope 
of the invention as set forth in the following claims.