WO1990013920A1 - IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH Tc SUPERCONDUCTIVE THIN FILM - Google Patents

IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH Tc SUPERCONDUCTIVE THIN FILM Download PDF

Info

Publication number
WO1990013920A1
WO1990013920A1 PCT/US1990/001795 US9001795W WO9013920A1 WO 1990013920 A1 WO1990013920 A1 WO 1990013920A1 US 9001795 W US9001795 W US 9001795W WO 9013920 A1 WO9013920 A1 WO 9013920A1
Authority
WO
WIPO (PCT)
Prior art keywords
thin film
homologous
superconductive
substrate
film
Prior art date
Application number
PCT/US1990/001795
Other languages
French (fr)
Inventor
Eliezer Wiener-Avnear
James E. Mcfall
Original Assignee
Hughes Aircraft Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hughes Aircraft Company filed Critical Hughes Aircraft Company
Publication of WO1990013920A1 publication Critical patent/WO1990013920A1/en

Links

Classifications

    • 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
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/28—Vacuum evaporation by wave energy or particle radiation
    • 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 copper oxide superconductor layers
    • H10N60/0521—Processes for depositing or forming copper oxide superconductor layers by pulsed laser deposition, e.g. laser sputtering

Definitions

  • the present invention generally relates to supercon ⁇ ductive materials, and more specifically to the formation 5 of thin layers of modified perovskite superconductive materials on insulative and semiconductive substrates using in-situ laser deposition.
  • Microelectronic devices may be made to operate at greatly increased speeds using intercon ⁇ nects patterned from superconductive films.
  • Josephson junctions consisting of two superconductive layers separ ⁇ ated by a thin insulative layer which acts as a "weak link", produce a tunnel effect which can serve as the basis for a multitude of extremely high speed microelectronic devices including memory and logic elements. Entire computers made from integrated Josephson junction devices will enable speed and power which is far beyond the current state of the art.
  • perovskite based superconductors especially including YBa 2 Cu 3 0 7 .
  • ⁇ yttrium-barium-copper oxide or YBCO
  • T c critical or Curie temperature
  • HTS high T c superconductors
  • YBCO gallium arsenide
  • the perovskite group of materials further includes insulators, with single crystal (100) strontium titanate (STO) , being of particular interest due to the close correlation of its thermal expansion and lattice constants with YBCO and their low chemical affinity.
  • Thin films of YBCO have been grown on single crystal, bulk substrates of STO using laser deposition as reported in "Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition", by T. Venkatesan, J. Appl. Phys. 63 (9), 1 May 1988, pp. 4591-4598.
  • thin films of modified perovskite superconductors and insulators have not been successfully formed on other types of materials, especially including those which are in widespread use as substrates in microelectronic devices.
  • the present invention enables the utilization of conventional integrated circuit substrates, including silicon, silicon-on-sapphire (SOS) and gallium arsenide, for the growth of HTS films.
  • SOS silicon-on-sapphire
  • This is accomplished by utilizing in-situ laser deposition of a thin film of a perovskite homologous material, preferably STO, on the substrate as an interlayer or buffer.
  • a thin film of superconductive material, preferably YBCO is formed on the STO film using the same method. With the thermal expansion coefficients and lattice constants of the two materials being closely matched, the quality of the superconductive layer is comparable to that of bulk YBCO.
  • the in-situ, laser deposition method eliminates exposure to the atmosphere which would degrade the super ⁇ conductive surfaces.
  • the laser deposition enables a 1:1 stoichiometric relationship between a pellet of a perov- skite material and a thin film of the material ablated from the pellet by the laser and deposited on the substrate. This enables direct deposition of STO on a conventional microelectronic device substrate which can be utilized by itself or as a virgin buffer layer for deposition of YBCO thin films.
  • YBCO surfaces are very sensitive to the environment, especially C0 2 in the atmosphere. Even very short exposure to the environment usually destroys the first atomic layer of a YBCO film. It is another feature of the invention to form an STO layer on a YBCO layer to act as a passivation layer and to protect the YCBO layer from the atmosphere.
  • the present method enables the formation of Josephson junction devices having two, three or more alternating superconductive and insulative layers on conventional substrates, due to the minimization of thermal stresses, crystallographic dislocations, and impurity interdiffusion between the layers.
  • FIG. 1 is a diagram illustrating a laser deposition apparatus for practicing the method of the present inven ⁇ tion
  • FIG. 2 is a diagram illustrating a material embodying the invention including thin films of perovskite homologous and superconductive materials formed on a substrate;
  • FIG. 3 is similar to FIG. 2, but further illustrates a second homologous film formed on the superconductive film.
  • FIG. 4 is a diagram illustrating a Josephson junction formed on a substrate in accordance with the invention.
  • a laser deposition apparatus for practicing the present invention is generally designated as 10 and includes a laser 12 for producing a beam 14 of coherent light.
  • the beam 14 passes through an optical system which is symbolically illustrated as a converging lens 16 into a housing 18 which is evacu ⁇ ated to a desired degree of low pressure by a vacuum pump 20.
  • holders 22 and 24 Disposed inside the housing 18 are holders 22 and 24 which fixedly retain pellets 26 and 28 of perovskite homologous and superconductive materials respectively.
  • the homologous material 26 is preferably STO whereas the superconductive material 28 is preferably YBCO.
  • a changer/rotator mechanism 30 for moving a desired one of the holders 22 and 24 into an operative position in the path of the laser beam 14 and rotating the holder and pellet at a desired angular speed. As viewed in FIG. 1, the holder 22 is in the operative position with the laser beam 14 incident on the STO pellet 26.
  • the laser beam 14 impinges on the pellet 26 or 28, causing the creation of a plume 32 of material ablated from the pellet.
  • a substrate 34 of a desired material such as silicon, sapphire, SOS, gallium arsenide, single crystal- line STO, or other modified perovskite material is fixedly mounted on a holder 36 which is rotated in a heater or open oven 38 to achieve uniform deposition.
  • the holder 36 is disposed in the path of the plume 32 such that material ablated from the pellet 26 or 28 by the laser beam 14 is deposited uniformly on the substrate 34.
  • Further illus ⁇ trated is a source 40 for supplying supplemental oxygen or other volatile substance to the substrate 34 in the oven 38 as required by the deposition process.
  • a preferred material 50 produced by the apparatus 10 is illustrated in FIG. 2.
  • the material 50 includes a substrate 52 which corresponds to the substrate 34 prior to deposition of material thereon.
  • a thin film 54 of perov ⁇ skite homologous material ablated from the pellet 26, and a thin film 56 of a modified perovskite superconductive material ablated from the pellet 28 are deposited on the substrate 52.
  • the thickness of the homologous film 54 is on order of 100 to 500 angstroms, whereas the thickness of the YBCO film 56 is typically 2000 - 10,000 angstroms.
  • the homologous film 54 has low chemical affinity, close crys- tallographic structure, has thermal expansion and lattice constants which are closely matched to those of the super ⁇ conductive film 56, and acts as an interlayer or buffer between the substrate 52 and the film 56. Strain of the superconductive film 56 due to a difference in thermal expansion coefficients between the film 56 and the sub ⁇ strate 52 is minimized by the matched interlayer film 54. The matched lattice constants of the films 54 and 56 minimize crystallographic dislocations from forming in the superconductive film 56. Experimental results have indi ⁇ cated that the properties of a YBCO film 56 produced in accordance with the embodiment of FIG. 2 are close to bulk YBCO.
  • the homologous interlayer film 54 prevents chemical reaction and/or interdiffusion of impurity mater- ials between the substrate 52 and superconductive film 56, thereby enabling the formation of a pure superconductive film at high temperatures which would produce interdif- fusion if the homologous interlayer film 54 were not present.
  • the degree of matching of the homologous and supercon ⁇ ductive materials required to practice the present inven ⁇ tion is dependent on numerous variables. In the exemplary case of YBCO on STO, the crystallographic mismatch is approximately 2.1%, and the thermal expansion coefficient mismatch is approximately 15%. Closer matching is of course desirable.
  • the laser 12 may typically produce a pulsed beam 14 having a wavelength of 248 nm, repetition rate of 1 to 10 Hz and pulse duration of 30 to 40 ns.
  • An exemplary practi ⁇ cal energy fluence of the laser beam 14 is 1 to 2 Joules/cm 2 .
  • the pressure in the housing 18 is typically 10 "1 to 10 " * Torr, with the temperature in the oven 38 being 500 - 700°C.
  • the apparatus 10 deposits the layers 54 and 56 on the substrate 52 in-situ.
  • the housing 18 is evacuated and the oven 38 brought up to the desired temper ⁇ ature, the environment in the vicinity of the substrate 34 is maintained constant during deposition of materials from the pellets 26 and 28.
  • the pellet 26 of homologous material is moved to the operative position and the film 54 is deposited on the substrate 52.
  • the changer mechanism 30 is activated and the positions of the holders 22 and 24 are switched from the relative positions il ⁇ lustrated in FIG. 1 so that the pellet 28 is in the opera ⁇ tive position.
  • the film 56 is then deposited on the substrate 52.
  • the operation of the changer mechanism 30 is sufficiently fast that it can be considered instantaneous for practical purposes.
  • the laser deposition process enables transfer of perovskite materials from pellets to a substrate with a 1:1 stoichiometric relationship. This enables a film of STO or other homologous material to be formed on a sub- strate with, for example, a larger thickness on the order of 3,000 - 10,000 angstroms, to facilitate the formation of optoelectronic devices on conventional substrates.
  • YBCO is a material including four components which tend to react with air, particularly the carbon dioxide component thereof.
  • a material 60 illustrated in FIG. 3 further includes a second homologous film 62 of STO formed on top of the YBCO film 56 by in-situ laser deposition.
  • the STO film 62 consti- tutes a passivation layer for the YBCO film 56, isolating the film 56 from the atmosphere.
  • the film 62 may be made sufficiently thick that useful microelectronic devices may be formed therein.
  • a material 70 of the invention which is illustrated in FIG. 4 includes the substrate 52, on which is formed a thin, homologous, insulative film 54, and a thin superconductive film 56 as in the embodiment of FIG. 2.
  • the material 70 further includes a second homolo- gous film 72, similar to the film 54, formed on the film 56.
  • any number of alternating homologous insulative and superconductive films may be formed on top of the material 70 within the scope of the present invention to constitute a plurality of vertical Josephson junctions. If STO or a similar single crystal perovskite material which is closely matched to YBCO is used as the substrate 52, the interlayer or buffer film 54 may be omitted and the YBCO film 56 formed directly on the substrate. It is further within the scope of the present invention to substitute a homologous semiconductive material for the insulative material in the films 54 and 72.
  • the in-situ laser deposition method of the present invention ensures the integrity of the Josephson junction surfaces, by minimizing environmental contamination and/or interdiffusion of materials between the sandwiched layers and providing thermal and crystallographic matching between the layers. While several illustrative embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art, without departing from the spirit and scope of the invention. For example, lanthanum aluminate (LaA10 3 ) may be substituted for STO as the perovskite homologous material. Accordingly, it is intended that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Manufacturing & Machinery (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)

Abstract

A thin film interlayer of a modified perovskite homologous material such as strontium titanate is formed by in-situ laser deposition on a semiconductive or insulative substrate (52). A thin film of a perovskite superconductive material (56) such as yttrium-barium-copper oxide is formed on the homologous thin film (54). The two perovskite materials have low chemical affinity and closely matched thermal and lattice constants, with the pre-deposited homologous film acting as a thermal, crystallographic and chemical buffer between the substrate and superconductive layer. Josephson junctions may be formed of alternating layers of the homologous material, which is an insulator, and the superconductive material. The in-situ laser deposition method enables a 1:1 stoichiometric relationship between a pellet of a perovskite material, and a thin film of the perovskite material ablated from the pellet by the laser and deposited on the substrate.

Description

IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH
Tc SUPERCONDUCTIVE THIN FIIM
BACKGROUND OF THE INVENTION Field of the Invention
The present invention generally relates to supercon¬ ductive materials, and more specifically to the formation 5 of thin layers of modified perovskite superconductive materials on insulative and semiconductive substrates using in-situ laser deposition.
Description of the Related Art 0 Thin films of superconductive materials formed on semiconductive and insulative substrates have widespread potential applications. Microelectronic devices may be made to operate at greatly increased speeds using intercon¬ nects patterned from superconductive films. Josephson junctions, consisting of two superconductive layers separ¬ ated by a thin insulative layer which acts as a "weak link", produce a tunnel effect which can serve as the basis for a multitude of extremely high speed microelectronic devices including memory and logic elements. Entire computers made from integrated Josephson junction devices will enable speed and power which is far beyond the current state of the art.
The discovery of perovskite based superconductors, especially including YBa2Cu307.ε (yttrium-barium-copper oxide or YBCO) has raised expectations not only of a new mechan¬ ism of superconductivity, but also of potential applica- tionε in advanced materials based technologies as well as microelectronics and hybrid opto-electronics. YBCO has a high Tc (critical or Curie temperature) on the order of 4°K and a zero resistance temperature above 84°K. Numerous attempts have been made to grow thin films of high Tc superconductors (HTS) including YBCO on materials including silicon, sapphire, and gallium arsenide which are used as substrates in microelectronic devices. The results have been unsatisfactory due to thermal and lattice con- εtant mismatches between the superconductive and substrate materials and interdiffusion of impurities between the materials at the high temperatures of thin film growth.
The perovskite group of materials further includes insulators, with single crystal (100) strontium titanate (STO) , being of particular interest due to the close correlation of its thermal expansion and lattice constants with YBCO and their low chemical affinity. Thin films of YBCO have been grown on single crystal, bulk substrates of STO using laser deposition as reported in "Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition", by T. Venkatesan, J. Appl. Phys. 63 (9), 1 May 1988, pp. 4591-4598. However, thin films of modified perovskite superconductors and insulators have not been successfully formed on other types of materials, especially including those which are in widespread use as substrates in microelectronic devices.
SUMMARY OF THE INVENTION
The present invention enables the utilization of conventional integrated circuit substrates, including silicon, silicon-on-sapphire (SOS) and gallium arsenide, for the growth of HTS films. This is accomplished by utilizing in-situ laser deposition of a thin film of a perovskite homologous material, preferably STO, on the substrate as an interlayer or buffer. A thin film of superconductive material, preferably YBCO, is formed on the STO film using the same method. With the thermal expansion coefficients and lattice constants of the two materials being closely matched, the quality of the superconductive layer is comparable to that of bulk YBCO.
The in-situ, laser deposition method eliminates exposure to the atmosphere which would degrade the super¬ conductive surfaces. The laser deposition enables a 1:1 stoichiometric relationship between a pellet of a perov- skite material and a thin film of the material ablated from the pellet by the laser and deposited on the substrate. This enables direct deposition of STO on a conventional microelectronic device substrate which can be utilized by itself or as a virgin buffer layer for deposition of YBCO thin films.
YBCO surfaces are very sensitive to the environment, especially C02 in the atmosphere. Even very short exposure to the environment usually destroys the first atomic layer of a YBCO film. It is another feature of the invention to form an STO layer on a YBCO layer to act as a passivation layer and to protect the YCBO layer from the atmosphere.
The present method enables the formation of Josephson junction devices having two, three or more alternating superconductive and insulative layers on conventional substrates, due to the minimization of thermal stresses, crystallographic dislocations, and impurity interdiffusion between the layers.
These and other features and advantages of the present invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings, in which like reference numerals refer to like parts.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a laser deposition apparatus for practicing the method of the present inven¬ tion;
FIG. 2 is a diagram illustrating a material embodying the invention including thin films of perovskite homologous and superconductive materials formed on a substrate;
FIG. 3 is similar to FIG. 2, but further illustrates a second homologous film formed on the superconductive film; and
FIG. 4 is a diagram illustrating a Josephson junction formed on a substrate in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1 of the drawings, a laser deposition apparatus for practicing the present invention is generally designated as 10 and includes a laser 12 for producing a beam 14 of coherent light. The beam 14 passes through an optical system which is symbolically illustrated as a converging lens 16 into a housing 18 which is evacu¬ ated to a desired degree of low pressure by a vacuum pump 20.
Disposed inside the housing 18 are holders 22 and 24 which fixedly retain pellets 26 and 28 of perovskite homologous and superconductive materials respectively. The homologous material 26 is preferably STO whereas the superconductive material 28 is preferably YBCO. Further illustrated is a changer/rotator mechanism 30 for moving a desired one of the holders 22 and 24 into an operative position in the path of the laser beam 14 and rotating the holder and pellet at a desired angular speed. As viewed in FIG. 1, the holder 22 is in the operative position with the laser beam 14 incident on the STO pellet 26.
The laser beam 14 impinges on the pellet 26 or 28, causing the creation of a plume 32 of material ablated from the pellet. A substrate 34 of a desired material such as silicon, sapphire, SOS, gallium arsenide, single crystal- line STO, or other modified perovskite material is fixedly mounted on a holder 36 which is rotated in a heater or open oven 38 to achieve uniform deposition. The holder 36 is disposed in the path of the plume 32 such that material ablated from the pellet 26 or 28 by the laser beam 14 is deposited uniformly on the substrate 34. Further illus¬ trated is a source 40 for supplying supplemental oxygen or other volatile substance to the substrate 34 in the oven 38 as required by the deposition process. A preferred material 50 produced by the apparatus 10 is illustrated in FIG. 2. The material 50 includes a substrate 52 which corresponds to the substrate 34 prior to deposition of material thereon. A thin film 54 of perov¬ skite homologous material ablated from the pellet 26, and a thin film 56 of a modified perovskite superconductive material ablated from the pellet 28 are deposited on the substrate 52. The thickness of the homologous film 54 is on order of 100 to 500 angstroms, whereas the thickness of the YBCO film 56 is typically 2000 - 10,000 angstroms. The homologous film 54 has low chemical affinity, close crys- tallographic structure, has thermal expansion and lattice constants which are closely matched to those of the super¬ conductive film 56, and acts as an interlayer or buffer between the substrate 52 and the film 56. Strain of the superconductive film 56 due to a difference in thermal expansion coefficients between the film 56 and the sub¬ strate 52 is minimized by the matched interlayer film 54. The matched lattice constants of the films 54 and 56 minimize crystallographic dislocations from forming in the superconductive film 56. Experimental results have indi¬ cated that the properties of a YBCO film 56 produced in accordance with the embodiment of FIG. 2 are close to bulk YBCO. Further, the homologous interlayer film 54 prevents chemical reaction and/or interdiffusion of impurity mater- ials between the substrate 52 and superconductive film 56, thereby enabling the formation of a pure superconductive film at high temperatures which would produce interdif- fusion if the homologous interlayer film 54 were not present. The degree of matching of the homologous and supercon¬ ductive materials required to practice the present inven¬ tion is dependent on numerous variables. In the exemplary case of YBCO on STO, the crystallographic mismatch is approximately 2.1%, and the thermal expansion coefficient mismatch is approximately 15%. Closer matching is of course desirable. However, a larger degree of mismatch is possible within the scope of the present invention if the deposition variables are suitably adjusted to produce a superconductive film of acceptable quality. The laser 12 may typically produce a pulsed beam 14 having a wavelength of 248 nm, repetition rate of 1 to 10 Hz and pulse duration of 30 to 40 ns. An exemplary practi¬ cal energy fluence of the laser beam 14 is 1 to 2 Joules/cm2. The pressure in the housing 18 is typically 10"1 to 10"* Torr, with the temperature in the oven 38 being 500 - 700°C.
In accordance with an important feature of the present invention, the apparatus 10 deposits the layers 54 and 56 on the substrate 52 in-situ. Once the housing 18 is evacuated and the oven 38 brought up to the desired temper¬ ature, the environment in the vicinity of the substrate 34 is maintained constant during deposition of materials from the pellets 26 and 28. First, the pellet 26 of homologous material is moved to the operative position and the film 54 is deposited on the substrate 52. Then, the changer mechanism 30 is activated and the positions of the holders 22 and 24 are switched from the relative positions il¬ lustrated in FIG. 1 so that the pellet 28 is in the opera¬ tive position. The film 56 is then deposited on the substrate 52. The operation of the changer mechanism 30 is sufficiently fast that it can be considered instantaneous for practical purposes.
With the vacuum level in the housing 18, temperature in the oven 38, intensity, wavelength and repetition rate of the laser beam 14, and other relevant conditions suitab¬ ly selected, the laser deposition process enables transfer of perovskite materials from pellets to a substrate with a 1:1 stoichiometric relationship. This enables a film of STO or other homologous material to be formed on a sub- strate with, for example, a larger thickness on the order of 3,000 - 10,000 angstroms, to facilitate the formation of optoelectronic devices on conventional substrates.
YBCO is a material including four components which tend to react with air, particularly the carbon dioxide component thereof. In order to protect the integrity of a YBCO film formed in accordance with the invention, a material 60 illustrated in FIG. 3 further includes a second homologous film 62 of STO formed on top of the YBCO film 56 by in-situ laser deposition. The STO film 62 consti- tutes a passivation layer for the YBCO film 56, isolating the film 56 from the atmosphere. If desired, the film 62 may be made sufficiently thick that useful microelectronic devices may be formed therein.
As discussed above, Josephson junctions, consisting of two superconductive films separated by a thin insulative film, create the possibility of tremendous advancements in computer and general microelectronic device technology. We envision the present invention to enable the formation of stable and reproducible Josephson junctions for fabrica- tion of useful devices. A material 70 of the invention which is illustrated in FIG. 4 includes the substrate 52, on which is formed a thin, homologous, insulative film 54, and a thin superconductive film 56 as in the embodiment of FIG. 2. The material 70 further includes a second homolo- gous film 72, similar to the film 54, formed on the film 56. A second thin superconductive film 74, similar to the film 56, is formed on the film 72. If desired, any number of alternating homologous insulative and superconductive films may be formed on top of the material 70 within the scope of the present invention to constitute a plurality of vertical Josephson junctions. If STO or a similar single crystal perovskite material which is closely matched to YBCO is used as the substrate 52, the interlayer or buffer film 54 may be omitted and the YBCO film 56 formed directly on the substrate. It is further within the scope of the present invention to substitute a homologous semiconductive material for the insulative material in the films 54 and 72.
The in-situ laser deposition method of the present invention ensures the integrity of the Josephson junction surfaces, by minimizing environmental contamination and/or interdiffusion of materials between the sandwiched layers and providing thermal and crystallographic matching between the layers. While several illustrative embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art, without departing from the spirit and scope of the invention. For example, lanthanum aluminate (LaA103) may be substituted for STO as the perovskite homologous material. Accordingly, it is intended that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.

Claims

WE CLAIM:
1. A method of forming a thin film of a superconduc¬ tive material on a substrate, comprising the steps of:
(a) in-situ laser deposition on the substrate of a thin film of a homologous material having low chemical affinity and thermal and lattice constants closely matched to the superconductive material; and
(b) in-situ laser deposition of a thin film of the superconductive material on the thin film of the homologous material.
2. A method as in claim 1, in which the substrate is formed of an electrically insulative material.
3. A method as in claim 2, in which the electrically insulative material comprises a homologous perovskite single crystal.
4. A method as in claim 2, in which the electrically insulative material is sapphire.
5. A method as in claim 1, in which the substrate is formed of an electrically semiconductive material.
6. A method as in claim 5, in which the semiconduc¬ tive material is selected from the group consisting of silicon and gallium arsenide.
7. A method as in claim 1, in which the homologous material has a modified perovskite structure.
8. A method as in claim 1, in which the homologous material is selected from the group consisting of strontium titanate and lanthanum aluminate.
9. A method as in claim 1, in which the superconduc¬ tive material has a modified perovskite structure.
10. A method as in claim 1, in which the supercon¬ ductive material is yttrium-barium-copper oxide.
11. A method as in claim 1, in which the homologous material is strontium titanate and the superconductive material is yttrium-barium-copper oxide, further comprising the step of: (c) in-situ laser deposition of a second film of the homologous material on the thin film of the supercon¬ ductive material.
12. A method of forming a Josephson junction on a substrate, comprising the steps of:
(a) in-situ laser deposition of a first thin film of a homologous, electrically insulative material on the substrate;
(b) in-situ laser deposition on the first thin film of the insulative material of a first thin film of a superconductive material having thermal and lattice con¬ stants closely matched to the insulative material; (c) in-situ laser deposition on the first thin film of the superconductive material of a second thin film of the insulative material; and
(d) in-situ laser deposition on the second thin film of the insulative material of a second thin film of the superconductive material; said thin films in combination constituting the Josephson junction.
13. A material comprising: a substrate; a thin film of homologous material formed on the substrate; and a thin film of a superconductive material formed on the thin film of the homologous material, the supercon¬ ductive material having thermal and lattice constants closely matched to the homologous material.
14. A material as in claim 13, in which the substrate comprises an electrically insulative material.
15. A material as in claim 13, in which the substrate comprises sapphire.
16. A material as in claim 13, in which the substrate comprises an electrically semiconductive material.
17. A material as in claim 13, in which the substrate comprises a material selected from the group consisting of silicon and gallium arsenide.
18. A material as in claim 13, in which the homolo¬ gous material has a perovskite structure.
19. A material as in claim 13, in which the homolo¬ gous material is selected from the group consisting of strontium titanate and lanthanum aluminate.
20. A material as in claim 13, in which the supercon¬ ductive material has a perovskite structure.
21. A material as in claim 13, in which the supercon¬ ductive material is yttrium-barium-copper oxide.
22. A material as in claim 13, in which the homolo¬ gous material is strontium titanate and the superconductive material is yttrium-barium-copper-oxide, the material further comprising a second film of the homologous material formed on the thin film of the superconductive material.
23. A material having a Josephson junction, compris¬ ing: a substrate; a first thin film of a homologous, electrically insulative material formed on the substrate; a first thin film of a superconductive material having a low chemical affinity and thermal and lattice constants closely matched to the insulative material formed on the first thin film of the insulative material; a second thin film of the insulative material formed on the first thin film of the superconductive material; and a second thin film of the superconductive mater¬ ial formed on the second thin film of the insulative material; said thin films in combination constituting the Josephson junction.
24. A material as in claim 23, in which the insula¬ tive material is strontium titanate and the superconductive material is yttrium-barium-copper oxide.
25. A material having a Josephson junction, compris¬ ing: a substrate formed of a single crystal of a homologous, electrically insulative material; a first thin film of a superconductive material having a low chemical affinity and thermal and lattice constants closely matched to the insulative material of the substrate; a thin film of the insulative material formed on the first thin film of the superconductive material; and a second thin film of the superconductive mater¬ ial formed on the thin film of the insulative material; said thin films in combination constituting the Josephson junction.
PCT/US1990/001795 1989-05-04 1990-04-04 IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH Tc SUPERCONDUCTIVE THIN FILM WO1990013920A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US34822289A 1989-05-04 1989-05-04
US348,222 1989-05-04

Publications (1)

Publication Number Publication Date
WO1990013920A1 true WO1990013920A1 (en) 1990-11-15

Family

ID=23367101

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1990/001795 WO1990013920A1 (en) 1989-05-04 1990-04-04 IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH Tc SUPERCONDUCTIVE THIN FILM

Country Status (1)

Country Link
WO (1) WO1990013920A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0445350A2 (en) * 1990-03-09 1991-09-11 The Regents Of The University Of California Microelectronic superconducting crossover and coil

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0292959A2 (en) * 1987-05-26 1988-11-30 Sumitomo Electric Industries Limited Superconducting member
EP0341520A1 (en) * 1988-05-11 1989-11-15 Siemens Aktiengesellschaft Process for the production of a layer of metal oxide supraconductor material by laser evaporation

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0292959A2 (en) * 1987-05-26 1988-11-30 Sumitomo Electric Industries Limited Superconducting member
EP0341520A1 (en) * 1988-05-11 1989-11-15 Siemens Aktiengesellschaft Process for the production of a layer of metal oxide supraconductor material by laser evaporation

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Applied Physics Letters, Volume 53, No. 20, 14 November 1988, American Institute of Physics, (New York, US), S. MIURA et al.: "Epitaxial Y-Ba-Cu-O Films on Si with Intermediate Layer by rf Magnetron Sputtering", pages 1967-1969 *
Applied Physics Letters, Volume 53, No. 3, 18 July 1988, American Institute of Physics, (New York, US), T. VENKATESAN et al.: "Superconducting Y1BA2CU3O7-x Films on Si", pages 243-245 *
Applied Physics Letters, Volume 54, No. 8, 20 February 1989, American Institute of Physics, (New York, US), X.D. WU et al.: "High Critical Currents in Epitaxial YBa2Cu3O7-x Thin Films on Silicon with Buffer Layers", pages 754-756 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0445350A2 (en) * 1990-03-09 1991-09-11 The Regents Of The University Of California Microelectronic superconducting crossover and coil
EP0445350A3 (en) * 1990-03-09 1991-12-11 The Regents Of The University Of California Microelectronic superconducting crossover and coil

Similar Documents

Publication Publication Date Title
Holzapfel et al. Off‐axis laser deposition of YBa2Cu3O7− δ thin films
US5077266A (en) Method of forming weak-link josephson junction, and superconducting device employing the junction
US5366953A (en) Method of forming grain boundary junctions in high temperature superconductor films
US4912087A (en) Rapid thermal annealing of superconducting oxide precursor films on Si and SiO2 substrates
US4882312A (en) Evaporation of high Tc Y-Ba-Cu-O superconducting thin film on Si and SiO2 with a zirconia buffer layer
JP2757284B2 (en) Method for producing metal oxide superconducting material layer by laser evaporation
EP0633331B1 (en) Process for preparing high crystallinity SrTiO3 oxide thin film
US4959346A (en) Composite with Y-BA-CU-O superconductive film
EP0635894B1 (en) Layered structure comprising insulator thin film and oxide superconductor thin film
WO1990013920A1 (en) IN-SITU LASER DEPOSITION OF HOMOLOGOUS FILM INTERLAYER FOR HIGH Tc SUPERCONDUCTIVE THIN FILM
Sobolewski et al. Patterning of thin-film high-T/sub c/circuits by the laser-writing method
KR100372889B1 (en) Ramp edge josephson junction devices and methods for fabricating the same
CA2212473C (en) Method for preparing layered structure including oxide superconductor thin film
Singh et al. I n situ deposition of BaF2 as a buffer layer and the superconducting thin films of Y‐Ba‐Cu‐O on silicon substrates by metalorganic chemical vapor deposition
US5438037A (en) Method for depositing another thin film on an oxide thin film having perovskite crystal structure
WO2005069392A1 (en) High-temperature superconductor devices and methods of forming the same
US5219830A (en) Process for preparing high-Tc superconducting integrated circuits
Reade et al. Ion-assisted pulsed-laser deposition for the fabrication of Y-Ba-Cu-O multilayer structures using oriented intermediate layers of YSZ and CeO2
JP2757257B2 (en) Method for forming oxide superconducting thin film
US4950644A (en) Method for the epitaxial preparation of a layer of a metal-oxide superconducting material with a high transition temperature
EP0402128B1 (en) Method of forming an oxide superconductor/semiconductor junction
Ford et al. Comparison of High-Temperature Superconductors in Multi-Chip Module Applications
JPH01100096A (en) Production of oxide superconductor thin film
Schaper et al. High Temperature Superconductor MCM Process Development
JPH0669561A (en) Semiconductor device and its manufacture

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB IT LU NL SE