WO1989007666A1 - Method of forming superconducting materials - Google Patents

Method of forming superconducting materials Download PDF

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Publication number
WO1989007666A1
WO1989007666A1 PCT/US1989/000225 US8900225W WO8907666A1 WO 1989007666 A1 WO1989007666 A1 WO 1989007666A1 US 8900225 W US8900225 W US 8900225W WO 8907666 A1 WO8907666 A1 WO 8907666A1
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organo
chamber
metallic compound
group
dpm
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PCT/US1989/000225
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French (fr)
Inventor
Tobin J. Marks
Klaus H. Dahmen
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Northwestern University
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/77—Preparation of chelates of aldehydes or ketones
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C49/00—Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
    • C07C49/92—Ketonic chelates
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F1/00—Compounds containing elements of Groups 1 or 11 of the Periodic System
    • C07F1/005—Compounds containing elements of Groups 1 or 11 of the Periodic System without C-Metal linkages
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F3/00—Compounds containing elements of Groups 2 or 12 of the Periodic System
    • C07F3/003—Compounds containing elements of Groups 2 or 12 of the Periodic System without C-Metal linkages
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic System
    • C07F5/003—Compounds containing elements of Groups 3 or 13 of the Periodic System without C-Metal linkages
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/408—Oxides of copper or solid solutions thereof
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
    • H10N60/0296—Processes for depositing or forming superconductor layers
    • H10N60/0436—Processes for depositing or forming superconductor layers by chemical vapour deposition [CVD]
    • H10N60/0464—Processes for depositing or forming superconductor layers by chemical vapour deposition [CVD] by metalloorganic chemical vapour deposition [MOCVD]

Definitions

  • This application relates to a method for forming superconducting materials through the use of chemical vapor deposition and more specifically, it involves a preparation of superconducting films through the use of metal organic chemical vapor deposition of volatile metal-organic complexes.
  • the recent discovery of metal oxide ceramic materials with relatively high superconducting transition temperatures gives rise to a large number of potential applications in advanced materials based technologies.
  • appropriate practical synthesis and processing methodologies for forming the superconductive ceramics are required for the use of superconducting materials in microelectronics and optoelectronics.
  • such superconductive ceramics may be formed as high-quality thin films which are deposited from the gas phase.
  • These thin films have in the past been deposited by evaporation techniques (ion-sputtering, electron beam, plasma, laser) which employ metal and metal oxide sources. All of these evaporation techniques require expensive energy-intensive equipment, must be carried out at high temperatures and do not provide consistently good quality films.
  • Metal-organic chemical vapor deposition has been used for depositing thin films of a vaporizable material.
  • volatile metal-organic precursors When using metal-organic chemical vapor deposition for depositing metal oxide films on substrates, volatile metal-organic precursors must be used; metal-organic precursors for the preparation of the known superconductive ceramic materials and which are stable in the gas phase are not generally available.
  • the chemical vapor deposition technique does offer the advantage, when compared to the physical methods of film preparation, of higher quality, smoother and more crystalline films produced at lower temperatures.
  • the metal precursor compounds In order to use metal-organic chemical vapor deposition, the metal precursor compounds must be sufficiently volatile to transport the compound as a gas to the substrate site. In addition, the metal precursor compound must be relatively stable in the gaseous state. Coordination number and coordinative saturation appear to play a major role in determining the volatility of neutrally charged metal-organics. In general, in low oxidation states, a metal complex with non-bulky ligands will attempt to expand its coordination number by coordinating additional ligands, or, when these are unavailable, by forming ligand bridging bonds to neighboring ions. Such bridging bonds lead to polymeric structure, high lattice energies, and low volatility. Two approaches can be used to circumvent this problem.
  • the metal In higher oxidation states, the metal will have a smaller ionic radius, hence a smaller desired coordination number, and generally more non-bridging ligands per metal ion. This usually leads to higher volatility.
  • Another way to reduce intermolecular interactions is by employing sterically bulky and/or fluorinated ligands. Also important, but apparently less critical, is keeping the molecular weight as low as possible.
  • the compounds selected for use in metal-organic chemical vapor deposition must be stable to the thermal conditions necessary to volatilize them.
  • the optimum manner for rendering metal complexes volatile should be complexation by bulk and/or multidentate non-polar hydrocarbon ligands, whic saturate the coordination sphere and prevent oligomerization.
  • Ligand fluorination further enhances volatility.
  • an object of the subject invention is a method of preparing a superconductive film by metal- organic chemical vapor deposition.
  • Another object of the subject invention is the use of volatile metal-organic complexes in the preparation of the superconductive material B 2C ⁇ i3 ⁇ 7_ ⁇ where M is yttrium or a lanthanide element, and ⁇ ⁇ l.
  • Still another object of the subject invention is the use of metal-organic chemical vapor deposition with a volatile copper organoligand, an yttrium organoligand, and a barium organoligand to form
  • metal organic copper complexes, lanthanide complexes, and barium complexes are vaporized or sublimed and caused to flow pass a heated substrate where they are deposited and transformed to form a high T c superconducting film of the formula MBa2Cu 3 ⁇ _5 where M is an element such as yttrium or a lanthanide element.
  • FIG. 1 is a schematic drawing of one type of an organic metal chemical vapor deposition apparatus which might be used in the method of the subject invention.
  • organo- etallics For film preparation of metals and their compounds, the following types of organo- etallics are generally used: Alkyl- and aryl- derivatives of metals, alkoxides and acetylacetonates , carbonyls, cyclopentadienyls, arene-derivatives, arene-carbonyls, and as suggested herein ⁇ -diketonates.
  • the mai requirements for such substances used for fil preparation are the following:
  • the organo-metallic should b transformable into the vapor phase without decomposition
  • the concentration of the organo-metallic vapor must b sufficient;
  • the organo-metallic decomposition must b gaseous and should not form side reactions which may lea to impurification of the film and to the formation o nonvolatile organic compounds;
  • the organo-metallic must be available nontoxic, and stable to oxygen and water at roo temperature.
  • Ligand systems which may be utilized in th subject invention to form the stable volatile meta organic compounds are ⁇ -diketonates of the formul
  • C(CH 3 ) 3 CF 3 are also relatively volatile.
  • C(CH 3 ) 3 CF 3 are also relatively volatile.
  • Type A M « Ln or Y, complexes with R « C(CH 3 ) 3
  • the apparatus for film deposition determines the film growth rate and the productivity of the deposition process.
  • the exact construction of the apparatus generally depends on the method of substrate heating, the geometry and the composition of the substrate, and the properties of the initial substances and requirements of the films to be prepared.
  • the chemical vapor deposition apparatus suitable for use in the method of the subject invention is shown at 10 and comprises evaporation chambers 12, 14 and 16 having external heating means, such as heating tape or other resistive heating means 18, 20 and 22 about the respective evaporation chambers 12, 14 and 16, all of which lead to the deposition or reaction chamber 32, which itself is surrounded by a resistive heating means, such as heat tape 24.
  • Other heat sources such as a radio frequency plasma or an intense light source, may be used.
  • the reaction chamber 32 is preferably constructed of quartz.
  • substrates 29 which may comprise SrTi0 3 , LiNb0 3 , AI2O3, Si 3 N 4 , Si ⁇ 2, MgO, platinum, gold, silver, or stainless steel. Passing through one of the evaporation chambers is a conduit for the introduction of oxygen and other reactants to the reaction chamber 32.
  • evaporation dishes 26, 27 and 28 are evaporation dishes 26, 27 and 28 in the respective evaporation chambers 12, 14, and 16. While shown as three separate evaporation chambers, it is possible that the evaporation chambers may be combined in one chamber.
  • the thermal decomposition of the respective organo-metallics on the substrate is accomplished in the following manner: Each different organo-metallic reagent is placed in the evaporator dish or reservoir. The entire assembly is flushed by an inert gas, such as nitrogen or argon. The evaporation chambers and reaction chambers are then heated to 300'C - 500'C, and a flow of oxidizing gas, such as 0 2 or tetrahydrofuran and/or a hydrolyzing gas, such as methanol or ethanol vapor is initiated into the reaction chamber while the chamber and substrate are maintained at that temperature. Water vapor may also be used in this stage, source flows of each composition are initiated when the organo-metallic is sublimed or otherwise vaporized.
  • an inert gas such as nitrogen or argon.
  • each organo-metallic is then transported to the heated substrate by natural convection or by the flow of the carrier gas.
  • the organo-metallics decompose into the formation of a continuous superconductive film of the composition MBa2Cu 3 ⁇ 7. ( ⁇ 1) .
  • the organo ligands remaining after deposition of the metal oxide onto th substrate may then be exhausted to a capture means. Th ligands thus captured may then be discarded or reused t form further metal organic ligands.
  • the evaporator dish temperature for each organo-metallic reagent is reduced to below the vaporizing or sublimation temperature of the organo-metallic, and the reactant gas flow is changed to pure oxygen at a flow rate of about 5 - 500 ml/ in. and preferably 100 ml/min. - 200 ml/min.
  • the substrate is heated to 600'C - 950*C to anneal the deposited metal oxide film and then allowed to slowly cool in the oxygen flow for a period of 1-24 hours.
  • the resulting superconductive film may be protected from atmospheric moisture or other contaminants by coating with a noble metal overlayer such as gold, silver, or platinum, or by treating with a silylating agent such as hexamethyldisilizane.
  • a noble metal overlayer such as gold, silver, or platinum
  • a silylating agent such as hexamethyldisilizane.
  • NH4OH is added to the resulting solution slowly to precipitate hydroxide, and neutralize the solution.
  • 0.15 mol (15.5 ml) of acetylacetone is added to the solution and the same is refluxed for 30 minutes.
  • the solution is cooled, filtered, and washed with hot water to remove unreacted acetylacetone. Drying in a vacuum desiccator yields Y(C 5 H 7 0 2 ) 3 .
  • a high T c superconductive ceramic of the formula MBa 2 Cu 3 ⁇ 7_5 may be obtained through procedures such as those in the following Examples III and IV.
  • Example IV Sufficient amounts of Cu(hfa) , ⁇ (C5H 7 0 )3, an
  • Ba(fod) 3 are each placed on an evaporator dish in a apparatus as described in connection with FIG. 1. Th evaporation and reaction chambers are purged with nitrogen. Each evaporator dish is heated to 180°C and oxygen is introduced through the oxygen feed tube at 200 ml/min. The reaction chamber temperature containing the substrate, being formed of Si0 2 , is maintained at SOO'C-SOO'C. After 5 hours of deposition of the metal oxide material, the substrate is heated to about 850'C to anneal the metal oxide material, and then allowed to cool slowly. The cooled metal oxide film, YBa 2 Cu 3 ⁇ 7_ $ ( 6 ⁇ 1) is treated with hexamethyldisilizane for protection from moisture.

Abstract

Metal organic copper complexes, lanthanide complexes, and barium complexes are sublimed (26, 27, 28) and caused to flow passed a heated substrate (29) where they are deposited and oxidized to form a high Tc superconducting film of the formula MBa2Cu3O7-delta where M is an element such a yttrium or a lanthanide element.

Description

METHOD OF FORMING SUPERCONDUCTING M&TERIAI-S
Background of the Invention This application relates to a method for forming superconducting materials through the use of chemical vapor deposition and more specifically, it involves a preparation of superconducting films through the use of metal organic chemical vapor deposition of volatile metal-organic complexes. The recent discovery of metal oxide ceramic materials with relatively high superconducting transition temperatures gives rise to a large number of potential applications in advanced materials based technologies. However, appropriate practical synthesis and processing methodologies for forming the superconductive ceramics are required for the use of superconducting materials in microelectronics and optoelectronics. One particularly desirable superconductor is LnBa2Cu3θ7_ δ (Ln = Y or lanthanide elements and δ < 1) . In general, such superconductive ceramics may be formed as high-quality thin films which are deposited from the gas phase. These thin films have in the past been deposited by evaporation techniques (ion-sputtering, electron beam, plasma, laser) which employ metal and metal oxide sources. All of these evaporation techniques require expensive energy-intensive equipment, must be carried out at high temperatures and do not provide consistently good quality films.
Metal-organic chemical vapor deposition has been used for depositing thin films of a vaporizable material. When using metal-organic chemical vapor deposition for depositing metal oxide films on substrates, volatile metal-organic precursors must be used; metal-organic precursors for the preparation of the known superconductive ceramic materials and which are stable in the gas phase are not generally available. However, the chemical vapor deposition technique does offer the advantage, when compared to the physical methods of film preparation, of higher quality, smoother and more crystalline films produced at lower temperatures.
In order to use metal-organic chemical vapor deposition, the metal precursor compounds must be sufficiently volatile to transport the compound as a gas to the substrate site. In addition, the metal precursor compound must be relatively stable in the gaseous state. Coordination number and coordinative saturation appear to play a major role in determining the volatility of neutrally charged metal-organics. In general, in low oxidation states, a metal complex with non-bulky ligands will attempt to expand its coordination number by coordinating additional ligands, or, when these are unavailable, by forming ligand bridging bonds to neighboring ions. Such bridging bonds lead to polymeric structure, high lattice energies, and low volatility. Two approaches can be used to circumvent this problem. In higher oxidation states, the metal will have a smaller ionic radius, hence a smaller desired coordination number, and generally more non-bridging ligands per metal ion. This usually leads to higher volatility. Another way to reduce intermolecular interactions is by employing sterically bulky and/or fluorinated ligands. Also important, but apparently less critical, is keeping the molecular weight as low as possible.
The compounds selected for use in metal-organic chemical vapor deposition must be stable to the thermal conditions necessary to volatilize them. In general, many of the properties which impart volatility afford in addition some resistance to thermal degradation, and therefore, the approaches which should foster higher volatility are also reasonable initial approaches to enhance thermal stability. As a result, the optimum manner for rendering metal complexes volatile should be complexation by bulk and/or multidentate non-polar hydrocarbon ligands, whic saturate the coordination sphere and prevent oligomerization. Ligand fluorination further enhances volatility.
Summary of the Invention
Accordingly, an object of the subject invention is a method of preparing a superconductive film by metal- organic chemical vapor deposition.
Another object of the subject invention is the use of volatile metal-organic complexes in the preparation of the superconductive material B 2CΛi3θ7_§ where M is yttrium or a lanthanide element, and δ < l.
Still another object of the subject invention is the use of metal-organic chemical vapor deposition with a volatile copper organoligand, an yttrium organoligand, and a barium organoligand to form
Figure imgf000005_0001
These and other objects of the subject invention are attained wherein metal organic copper complexes, lanthanide complexes, and barium complexes are vaporized or sublimed and caused to flow pass a heated substrate where they are deposited and transformed to form a high Tc superconducting film of the formula MBa2Cu3θ _5 where M is an element such as yttrium or a lanthanide element.
Brief Description of the Drawings FIG. 1 is a schematic drawing of one type of an organic metal chemical vapor deposition apparatus which might be used in the method of the subject invention.
Detailed Description of the Invention
For film preparation of metals and their compounds, the following types of organo- etallics are generally used: Alkyl- and aryl- derivatives of metals, alkoxides and acetylacetonates , carbonyls, cyclopentadienyls, arene-derivatives, arene-carbonyls, and as suggested herein β -diketonates. The mai requirements for such substances used for fil preparation are the following:
1. The organo-metallic should b transformable into the vapor phase without decomposition
The concentration of the organo-metallic vapor must b sufficient;
2. The organo-metallic decomposition must b gaseous and should not form side reactions which may lea to impurification of the film and to the formation o nonvolatile organic compounds; and
3. The organo-metallic must be available nontoxic, and stable to oxygen and water at roo temperature. Ligand systems which may be utilized in th subject invention to form the stable volatile meta organic compounds are β -diketonates of the formul
Figure imgf000006_0001
Copper complexes of type A (n = 2), with R = R1 = CH3 C(CH3)3 (dpm), or CF3 (hfa) and are quite volatile. Typ
A complexes of M * Ln or Y (n » 3) where R = R»
C(CH3)3 CF3 are also relatively volatile. In addition
Type A, M « Ln or Y, complexes with R « C(CH3)3
R* = CF2CF2CF3(fod) are far more volatile than those wit dpm. Volatile Type A complexes (n - 2) are prepared fo barium where (in order of increasing volatility) R = R1
C(CH3)3; R« - C(CH3)3, R = CF2CF2CF3; and R - R'
CF2CF3(dfh) . The following expressions will be use interchangeably hereinafter: Dipivaloylmethane complex - dpm « 2,2,6,6- tetramethyl-3 ,5-heptanedione ■ C 1H19θ2 Acetylacetone complex « C5H7O2 Hexaflouroacetylacetone complex = hfa =
CF3COCHCOCF3 = C5H02F6 C7HO2F10 - C2F5COCHCOC2F5 = dfh C4H9COCHCOC H9C3F7 = C14H1902F7 = fod Representative compounds useful in the subject invention and their respective sublimation temperatures are given below in Table I.
Table I Sublimation Temperature (*C)/ Compound Pressure (torr)
Cu(dpm)2 lOO'C/10"5
Cu(hfa)2 80'C/IO-5 Y(dpm)3 180'C/IO"5
Y(fod)3 140'C/IO'5
Ba(dpm)2 170'C/10~5
Ba(fod)3 170'C/IO"5
Ba(dfh)3 140*C/10"2 Y(C5H702)3 160'C/10"2
The apparatus for film deposition, to a great extent, determines the film growth rate and the productivity of the deposition process. The exact construction of the apparatus generally depends on the method of substrate heating, the geometry and the composition of the substrate, and the properties of the initial substances and requirements of the films to be prepared. As shown in FIG. 1, the chemical vapor deposition apparatus suitable for use in the method of the subject invention is shown at 10 and comprises evaporation chambers 12, 14 and 16 having external heating means, such as heating tape or other resistive heating means 18, 20 and 22 about the respective evaporation chambers 12, 14 and 16, all of which lead to the deposition or reaction chamber 32, which itself is surrounded by a resistive heating means, such as heat tape 24. Other heat sources, such as a radio frequency plasma or an intense light source, may be used. The reaction chamber 32 is preferably constructed of quartz. Within the reaction chamber are substrates 29 which may comprise SrTi03, LiNb03, AI2O3, Si3N4, Siθ2, MgO, platinum, gold, silver, or stainless steel. Passing through one of the evaporation chambers is a conduit for the introduction of oxygen and other reactants to the reaction chamber 32. Within each of the evaporation chambers, there are evaporation dishes 26, 27 and 28 in the respective evaporation chambers 12, 14, and 16. While shown as three separate evaporation chambers, it is possible that the evaporation chambers may be combined in one chamber.
Generally speaking, the thermal decomposition of the respective organo-metallics on the substrate is accomplished in the following manner: Each different organo-metallic reagent is placed in the evaporator dish or reservoir. The entire assembly is flushed by an inert gas, such as nitrogen or argon. The evaporation chambers and reaction chambers are then heated to 300'C - 500'C, and a flow of oxidizing gas, such as 02 or tetrahydrofuran and/or a hydrolyzing gas, such as methanol or ethanol vapor is initiated into the reaction chamber while the chamber and substrate are maintained at that temperature. Water vapor may also be used in this stage, source flows of each composition are initiated when the organo-metallic is sublimed or otherwise vaporized. The vapors of each organo-metallic are then transported to the heated substrate by natural convection or by the flow of the carrier gas. On the heated substrate, the organo-metallics decompose into the formation of a continuous superconductive film of the composition MBa2Cu3θ7. ( < 1) . The organo ligands remaining after deposition of the metal oxide onto th substrate may then be exhausted to a capture means. Th ligands thus captured may then be discarded or reused t form further metal organic ligands. In the second stage of deposition, the evaporator dish temperature for each organo-metallic reagent is reduced to below the vaporizing or sublimation temperature of the organo-metallic, and the reactant gas flow is changed to pure oxygen at a flow rate of about 5 - 500 ml/ in. and preferably 100 ml/min. - 200 ml/min. The substrate is heated to 600'C - 950*C to anneal the deposited metal oxide film and then allowed to slowly cool in the oxygen flow for a period of 1-24 hours. The resulting superconductive film may be protected from atmospheric moisture or other contaminants by coating with a noble metal overlayer such as gold, silver, or platinum, or by treating with a silylating agent such as hexamethyldisilizane. Representative examples for the preparation of a ligand complex for use in the present invention are as follows:
Example I Synthesis of Y(C5H7θ2)3ftrisfacetylacetonate) 1
0.05 mol of Y(N03)3 is dissolved in water.
NH4OH is added to the resulting solution slowly to precipitate hydroxide, and neutralize the solution. 0.15 mol (15.5 ml) of acetylacetone is added to the solution and the same is refluxed for 30 minutes. The solution is cooled, filtered, and washed with hot water to remove unreacted acetylacetone. Drying in a vacuum desiccator yields Y(C5H702)3.
Example II
Synthesis of Y.Cι:L ^gOg.? -Yfdpm)3 0.06 mol of dipivaloylmethane is dissolved in 30 ml of ethanol, and placed in a flask with a stopcock connected to an exhaust unit. 2.4 gr of NaOH is dissolved in 50 ml of 50% ethanol; the resulting solution is poured into the flask. The reaction product is continuously stirred by means of a magnetic stirrer. To this is added a solution obtained by dissolving 0.02 mol of Y(N03)3'6H2θ in 50 ml of 50% ethanol. The flask is placed under nitrogen and the solution stirred for 2 hours. It is then distilled under reduced pressure until the solution is reduced to half of its initial volume. 350 ml of a distilled water is added to separate a precipitate of Y(dpm)3, which is vacuum-filtered and dried. The crystals are re-crystallized under nitrogen from n-hexane, and vacuum-dried. Utilizing organo-metallic ligands such as listed above and which may be prepared according to procedures of Examples I and II, or which may be obtained from commercial sources, a high Tc superconductive ceramic of the formula MBa2Cu3θ7_5 may be obtained through procedures such as those in the following Examples III and IV.
Example III
Sufficient amounts of Cu(dpm)2/ Y(dpm)3, and Ba(dp )^ are each placed on an evaporator dish in an apparatus as described in connection with FIG. 1. The evaporation and reaction chambers are purged with nitrogen. Each evaporator dish is heated to 180*C and oxygen is introduced through the oxygen feed tube at 200 ml/min. The reaction chamber containing the deposition substrate, formed of Si02, is maintained at 300'C-500*C. After 10 hours of deposition of the metal complex, ' the substrate is heated to about 850"C to anneal the metal complex, and then allowed to cool slowly while the oxygen flow is maintained. The cooled metal complex, YBa2Cu307_ δ ( a < 1) is treated with hexamethyldisilizane for protection from moisture.
Example IV Sufficient amounts of Cu(hfa) , Ϊ(C5H70 )3, an
Ba(fod)3 are each placed on an evaporator dish in a apparatus as described in connection with FIG. 1. Th evaporation and reaction chambers are purged with nitrogen. Each evaporator dish is heated to 180°C and oxygen is introduced through the oxygen feed tube at 200 ml/min. The reaction chamber temperature containing the substrate, being formed of Si02, is maintained at SOO'C-SOO'C. After 5 hours of deposition of the metal oxide material, the substrate is heated to about 850'C to anneal the metal oxide material, and then allowed to cool slowly. The cooled metal oxide film, YBa2Cu3θ7_ $ ( 6 < 1) is treated with hexamethyldisilizane for protection from moisture.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments and equivalents falling within the scope of the appended claims.
Various features of the invention are set forth in the following claims.

Claims

WHAT IS CLAIMED:
1. A method for the preparation of a superconductive ceramic material by chemical vapor deposition comprising the steps of:
(a) flushing a first chamber with an inert gas;
(b) placing three organo-metallic compounds of the formula
in said chamber,
Figure imgf000012_0001
where R and R' are selected from the group consisting of -CH3, -C(CH3)3, -CF3, -CF2CF2CF3, and -CF2CF3, the first organo-metallic compound having M = Ba, the second organo-metallic compound having M = Cu, the second organo-metallic compound having M selected from the group consisting of yttrium and the lanthanide elements; (c) heating each organo-metallic compound to its vaporizing temperature to cause a source flow comprising a vapor of each organo-metallic compound in said first chamber;
(d) transporting said vapors into a second chamber;
(e) initiating a flow of oxygen into said second chamber;
(f) depositing film on a substrate in said second chamber; (g) terminating said source flow;
(h) increasing the temperature of said substrate to the range of 600*C - 950*C to thereby anneal said film; and
(i) whereby a ceramic of the formula LaBa2Cu307_ ξ ( δ < 1) is prepared, where La is selected from the group consisting of the lanthanide elements and yttrium.
2. The method of Claim 1 further including th steps of flushing three separate chambers and placin each of said three organo-metallic compounds in different one of said separate chambers.
3. The method of Claim 1 further including the step of adding water vapor to the second chamber wit said flow of oxygen.
4. The method of Claim 1 wherein the first organo-metallic compound is selected from the group consisting of:
Ba(fod)3, Ba(dfh)3, and Ba(dpm)2; the second organo-metallic compound is selected from the group consisting of Cu(dpm)2 and Cu(hfa)2; and the third organo-metallic compound is selected from the group consisting of Y(dpm)3, Y(fod)3, and Y(C5H702)3.
5. A method for the preparation of a superconductive ceramic material by chemical vapor deposition comprising the steps of:
(a) flushing three separated chambers with an inert gas;
(b) placing an organo-metallic compound of the formula
Figure imgf000013_0001
where R and R' are selected from the group consisting of -CH3, -C(CH3)3, -CF3, -CF2CF2CF3, and -CF2CF3, the first organo-metallic compound having M = Ba and being placed in a first chamber, the second organo-metallic compound having M = Cu and being placed in a second chamber, the second organo-metallic compound having M selected from the group consisting of yttrium and the lanthanide elements and being placed in a third chamber; (c) heating each organo-metallic compound to its vaporizing temperature to cause a source flow comprising a vapor of each organo-metallic compound in each respective chamber;
(d) transporting said vapors into a heated second chamber;
(e) initiating a flow of oxygen of about 180 - 200 ml/hr. into said second chamber;
(f) depositing a film on a substrate in said second chamber;
(g) terminating said source flow; (h) maintaining said oxygen flow; (i) increasing the temperature of said substrate to the range of 600*C - 950*C to thereby anneal said film; and"
(j) whereby a ceramic of the formula
MBa2Cu3θ7_ δ ( δ < 1) is prepared, where M is selected from the group consisting of the lanthanide elements and yttrium.
6. The method of Claim 5 further including the step of adding water vapor to the second chamber with said flow of oxygen.
7. The method of Claim 5 wherein the first organo-metallic compound is selected from the group consisting of:
Ba(fod)3, Ba(dfh)3, and Ba(dpm)2 the second organo-metallic compound is selected from the group consisting of Cu(dpm)2 and Cu(hfa) ; and the third organo-metallic compound is selected from the group consisting of Y(dpm)3, Y(fod)3f and Y(C5H702)3.
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US5183510A (en) * 1988-11-30 1993-02-02 Fujitsu Limited Apparatus and process for chemical vapor deposition
WO1991013185A3 (en) * 1990-03-02 1992-10-01 Hoechst Ag Device for producing films of mixed metal oxides
WO1991013185A2 (en) * 1990-03-02 1991-09-05 Hoechst Aktiengesellschaft Device for producing films of mixed metal oxides
FR2662164A1 (en) * 1990-05-18 1991-11-22 Centre Nat Rech Scient Heteropolymetallic complexes, their preparation and their use in the preparation of oxides, especially of superconducting oxides
EP0460627A1 (en) * 1990-06-05 1991-12-11 Air Products And Chemicals, Inc. Volatile crown ligand beta-diketonate alkaline earth metal complexes
US6126996A (en) * 1990-07-06 2000-10-03 Advanced Technology Materials, Inc. Metal complex source reagents for chemical vapor deposition
US5225561A (en) * 1990-07-06 1993-07-06 Advanced Technology Materials, Inc. Source reagent compounds for MOCVD of refractory films containing group IIA elements
US5453494A (en) * 1990-07-06 1995-09-26 Advanced Technology Materials, Inc. Metal complex source reagents for MOCVD
US5280012A (en) * 1990-07-06 1994-01-18 Advanced Technology Materials Inc. Method of forming a superconducting oxide layer by MOCVD
EP0508345A3 (en) * 1991-04-09 1994-06-01 Hoechst Ag Volatile alkaline earth complex and its application
EP0508345A2 (en) * 1991-04-09 1992-10-14 Hoechst Aktiengesellschaft Volatile alkaline earth complex and its application
EP0527661A1 (en) * 1991-08-14 1993-02-17 The Associated Octel Company Limited Metal beta-diketonates
WO1993004072A1 (en) * 1991-08-14 1993-03-04 The Associated Octel Company Limited METAL β-DIKETONATES
EP0563557A3 (en) * 1992-03-18 1994-04-20 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh
EP0563557A2 (en) * 1992-03-18 1993-10-06 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Volatile rate earth metal alkoxides, especially for the preparation of rare earth metal oxides, and alcohols for the synthesis of volatile compounds
WO1994017078A1 (en) * 1993-01-22 1994-08-04 Rhone-Poulenc Chimie Rare earth compounds and their preparation
US5504195A (en) * 1993-01-22 1996-04-02 Rhone-Poulenc Chimie Rare earth compounds and their preparation
WO1995014698A1 (en) * 1993-11-24 1995-06-01 The Associated Octel Company Limited Volatile organic lanthanide compounds and methods for the preparation of lanthanide-containing layered materials from these compounds
NL9302030A (en) * 1993-11-24 1995-06-16 Ass Octel Volatile yttrium organic compounds and process for the preparation of yttrium-containing layered materials from these compounds.
GB2298203A (en) * 1993-11-24 1996-08-28 Ass Octel Volatile organic lanthanide compounds and methods for the preparation of lanthanide-containing layered materials from these compounds
GB2298203B (en) * 1993-11-24 1998-06-17 Ass Octel Volatile organic lanthanide compounds and methods for the preparation of lanthanide-containing layered materials from these compounds
US5837321A (en) * 1993-11-24 1998-11-17 The Associated Octel Company Limited Volatile organic lanthanide compounds and methods for the preparation of lanthanide-containing layered materials form these compounds
FR3081868A1 (en) * 2018-06-05 2019-12-06 Compagnie Generale Des Etablissements Michelin PROCESS FOR THE PREPARATION OF ACETYLACETONATE FROM A HYDRATED OR ANHYDROUS CHEMICAL ELEMENT
WO2019234356A1 (en) * 2018-06-05 2019-12-12 Compagnie Generale Des Etablissements Michelin Method for producing acetylacetonate from a hydrated or anhydrous chemical element

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