Bismuth based oxide superconductor thin films and method of manufacturing the same
a superconductor and oxide technology, applied in the field of oxide superconductor, can solve the problems of current leakage, difficult to form a very thin uniform barrier layer, heat production, etc., and achieve the effect of superior performan
Inactive Publication Date: 2009-08-06
NAT INST OF ADVANCED IND SCI & TECH
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Benefits of technology
This approach enables the production of high-performance Josephson devices with enhanced critical current density and characteristic parameters, overcoming the limitations of existing methods by achieving well-crystallized a-axis oriented Bi-based oxide superconductor thin films.
Problems solved by technology
In addition to the high speed switching, the Josephson device shows a small heat production than a high density integrated circuit, in which heat production is a problem common to semiconductor devices.
A problem that requires a breakthrough in order to realize manufacturing of a layered Josephson junction using an oxide superconductor, is closely related to the crystal structure of oxide superconductors.
However, in making a barrier layer very thin, a rough surface caused by deposit and so on becomes a problem, which makes it difficult to form a very thin uniform barrier layer, and which causes current leakage between superconductors sandwiching the barrier layer from each side.
Therefore this type of Josephson junction has not been obtained yet.
Moreover, even if the Josephson junction can be formed, the Josephson critical current density Jc and the Josephson characteristic parameter IcRn are small, and good characteristics may not be obtained.
However, according to this method, the proportion of the c-axis that is parallel to the substrate varies depending on conditions, and it can not be said that a Bi-based oxide superconductor thin film of good quality can be obtained.
However, there is no disclosure of any specific process to obtain the good quality Bi-based oxide superconductor thin film whose c-axis is oriented parallel to the substrate and whose a-axis (or b-axis) is oriented perpendicular to the substrate.
Method used
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[0032]Using (110) crystal plane of LaSrAlO4 single crystal substrate, a well-crystallized a-axis oriented Bi-2223 superconductor thin film was manufactured by metal-organic chemical vapor deposition (MOCVD). The MOCVD device is shown in FIG. 3. The film was formed under the following conditions; Bi(C6H5)3, Sr(DPM)2, Ca(DPM)2, and Cu(DPM)2 (DPM: dipivaloylmethan) were used as metal-organic materials while each temperature was maintained at 72° C., 176° C., 161° C., and 80° C., respectively; the Ar carrier gas flow rate was 100, 300, 300, 70 sccm, respectively; the total pressure was 50 torr; the oxygen partial pressure was 23 torr; and the substrate temperature was 570° C.
[0033]The obtained X-ray diffraction pattern is shown FIG. 4. As it is clear from the figure, all of the diffraction peaks except for the substrate can be identified as the (n00) or (0n0) plane of the Bi-2223. According to this, it is confirmed that a Bi-2223 thin film whose c-axis is oriented parallel to the substr...
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Abstract
A Bi-based oxide superconductor thin film whose c-axis is oriented parallel to the substrate and whose a-axis (or b-axis) is oriented perpendicular to the substrate, is manufactured in order to obtain a high performance layered Josephson junction using a Bi-based oxide superconductor. The method of manufacturing an a-axis oriented Bi-based oxide superconductor thin film, involves an epitaxial growth process using an LaSrAlO4 single crystal substrate of a (110) plane or a LaSrGaO4 single crystal substrate of a (110) plane, for which the lattice constant matches well with a (100) plane of a Bi-2223 oxide superconductor. By this method, rather than the normally easily obtained Bi-2212, an a-axis oriented film of Bi-2223 showing an extremely high superconductive transition temperature even for a Bi-based oxide superconductor can be selectively manufactured.
Description
CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional of U.S. patent application Ser. No. 11 / 228,787, filed Sep. 16, 2005, in which benefit of and priority to is claimed to Japanese Patent Application No. 2004-273999, filed Sep. 21, 2004, and Japanese Patent Application No. 2005-090130, filed in Mar. 25, 2005, which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to an oxide superconductor with a c-axis oriented parallel to a substrate and an a-axis (or b-axis) oriented perpendicular to the substrate, especially to bismuth based (hereunder “Bi-based”) oxide superconductor thin films, specifically Bi2Sr2Ca2Cu3O10±X (where X is a positive number less than unity, hereunder “Bi-2223”) or Bi2Sr2CuO6±Y (where Y is a positive number less than unity, hereunder “Bi-2201”), in order to obtain a high performance layered Josephson junction using an oxide superconductor especially a Bi-based oxide superconductor, and a...
Claims
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IPC IPC(8): H01L39/22H01L39/24H01L39/12B32B9/00
CPCC30B25/02C30B25/18H01L39/2496H01L39/2458C30B29/22H10N60/0604H10N60/0941
InventorENDO, KAZUHIRO
OwnerNAT INST OF ADVANCED IND SCI & TECH