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(12) United States Patent (10) Patent N0.: US 7,736,761 B2 Foltyn Et A1

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(12) United States Patent (10) Patent N0.: US 7,736,761 B2 Foltyn Et A1 US007736761B2 (12) United States Patent (10) Patent N0.: US 7,736,761 B2 Foltyn et a1. (45) Date of Patent: Jun. 15, 2010 (54) BUFFER LAYER FOR THIN FILM (58) Field of Classi?cation Search ............... .. 505/230, STRUCTURES 505/237, 238; 428/699i702, 930; 174/1251; 427/62 (75) Inventors: Stephen R. Foltyn, Los Alamos, NM See application ?le for complete search history. (US); Quanxi Jia, Los Alamos, NM (56) References Cited (US); Paul N. Arendt, Los Alamos, NM (US); Haiyan Wang, Los Alamos, NM U.S. PATENT DOCUMENTS (Us) 6,410,487 B1 * 6/2002 Miller et a1. ........ .. 505/239 6,716,545 B1 * 4/2004 Holesinger et a1. 428/701 (73) Assignee: Los Alamos National Security, LLC, 6,756,139 B2 * 6/2004 Jia et a1. ............. .. 428/701 Los Alamos, NM (US) 6,800,591 B2 * 10/2004 Jia et a1. ......... .. 505/237 6,921,741 B2 * 7/2005 Arendt et a1. ............. .. 505/239 Notice: Subject to any disclaimer, the term of this FOREIGN PATENT DOCUMENTS patent is extended or adjusted under 35 WO 03/021656 * 3/2003 U.S.C. 154(b) by 182 days. * cited by examiner (21) Appl. No.: 11/591,269 Primary ExamineriSteven Bos Assistant ExamineriPaul A WartaloWicZ (22) Filed: Oct. 31, 2006 (74) Attorney, Agent, or FirmiBruce H. Cottrell; Juliet A. Jones (65) Prior Publication Data US 2010/0093547 A1 Apr. 15, 2010 (57) ABSTRACT A composite structure including a base substrate and a layer Related US. Application Data of a mixture of strontium titanate and strontium ruthenate is (62) Division of application No. 10/624,855, ?led on Jul. provided. A superconducting article can include a composite 21, 2003, noW Pat. No. 7,129,196. structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium (51) Int. Cl. titanate and strontium ruthenate and a top-layer of a super B32B 9/00 (2006.01) conducting material such as YBCO upon the buffer layer. (52) US. Cl. ..................... .. 428/701; 428/702; 428/930; 505/237; 505/238; 174/125.1 12 Claims, 2 Drawing Sheets 3.5 é‘ _ E 3 0 O E o E 2.5 * V 0 ‘a. O 2 7 co 0 . ‘U H C 1 .5 ‘ § § . 5 o 1 _ . E Q .2 I‘: 0l- 0.5 _ O 1 1 | 1 650 700 750 800 850 STO Deposition Temperature (C) US. Patent Jun. 15, 2010 Sheet 1 of2 US 7,736,761 B2 i— l u: E Q’ P“. c: to ‘I. I? c5 ’‘ . .2‘ LI. Q 5 c. I- *I4— —{ 1 w c: m. N w. '- w. I, WNW} iuswp ww-‘nvlmws US. Patent Jun. 15, 2010 Sheet 2 of2 US 7,736,761 B2 0mm cow N.mE omw 6vEBEQQEB558300.5 ooh 0mm N ‘- ‘D. O (ZLUOIVW) Mgsuap wanna wonyg US 7,736,761 B2 1 2 BUFFER LAYER FOR THIN FILM Wherein strontium titanate is suggested as a buffer layer hav STRUCTURES ing a moderate dielectric constant. Despite the many prior uses of both stronium ruthenate and RELATED APPLICATIONS stronium titanate, the use of stronium titanate alone or the use of a mixture of stronium ruthenate and stronium titanate as a This application is a divisional of patent application Ser. buffer layer has not been previously described upon an IBAD No. 10/624,855 ?led, Jul. 21, 2003 now US. Pat. No. 7,129, magnesium oxide layer in a coated conductor superconduct 196 issued Oct. 31, 2006. ing structure. Additionally, the use of a mixture of stronium ruthenate and stronium titanate as a buffer layer has not been STATEMENT REGARDING FEDERAL RIGHTS previously described as a layer in other electronic applica tions such as ferroelectric, ferromagnetic, piezoelectric and This invention Was made With government support under the like. Contract No. DE-AC52-06NA25396 aWarded by the US. It is an object of the present invention to provide composite Department of Energy. The government has certain rights in structures including a buffer layer of strontium titanate or a the invention. mixture of strontium titanate and strontium ruthenate (SrTixRul_xO3 Where 0<x§ 1) directly on a magnesium oxide FIELD OF THE INVENTION interlayer Where the buffer layer is suitable for subsequent groWth of a thin ?lm layer, e.g., a superconducting layer, thereon. The present invention relates to a buffer layer for thin ?lm 20 It is another object of the present invention to provide structures. Among such thin ?lm structures are included composite structures including a buffer layer of a mixture of superconducting structures, ferroelectric structures, photo strontium titanate and strontium ruthenate (SrTi,€Rul_,€O3 voltaic structures and others. The superconducting structures Where 0<x<1) Where the buffer layer is suitable for subse are those based upon YBa2Cu3O7 (Y BCO) as the supercon quent groWth of a thin ?lm layer thereon. ducter With a substrate of, e.g., single crystal substrates such 25 as lanthanum aluminum oxide, aluminum oxide, magnesium SUMMARY OF THE INVENTION oxide and the like, and polycrystalline substrates such as nickel-based alloys. The buffer layer is employed as a layer To achieve the foregoing and other objects, and in accor upon selected substrates. In the superconducting structures dance With the purposes of the present invention, as embodied commonly referred to as coated conductors, the buffer layer is 30 and broadly described herein, the present invention provides employed betWeen and aYBCO superconducting layer and a a composite structure including a base substrate, and a buffer base metal substrate having a magnesium oxide coated sub layer of SrTiXRuHCO3 Where 0<x<1 thereon the base sub strate, the magnesium oxide layer deposited in an ion beam strate. Such a composite structure can serve as a support for assisted deposition. For example, high temperature supercon deposition of subsequent high quality epitaxial thin ?lm lay ducting ?lms of YBCO can be groWn epitaxially on epitaxial 35 ers thereon. Such thin ?lm layers can be of materials such as structures including the present buffer layer and provide high high temperature superconducting materials, e. g., YBCO and Jc’s and Ic’s. the like, such as ferroelectric materials, e.g., barium strontium titanate, strontium bismuth tantalate and the like, such as BACKGROUND OF THE INVENTION ferromagnetic materials, e. g., lanthanum strontium mangan 40 ate, lanthanum calcium manganate and the like, such as The preparation of oriented layers of crystallographically pieZoelectric materials, e.g., lead Zirconium titanate and the materials is critical in a number of technical areas. For like, and other such materials, e.g., yttrium manganate, bis example, high temperature superconductors often employ muth ferrite or bismuth manganate. epitaxially oriented layers of, e.g., YBCO to achieve desired In one embodiment, the present invention provides a com properties. Similarly, epitaxially oriented ?lms such as con 45 posite structure including a base metallic substrate having a ductive oxides, ferroelectric, ferromagnetic, pieZoelectric, layer of magnesium oxide thereon, and a buffer layer of insulating, and semiconductive materials are desired in the SrTi,€Ru1_,€O3 Where 0<x§ 1 thereon the layer of magnesium areas of microelectric and opto-electric devices. To achieve oxide. In a preferred embodiment, the magnesium oxide layer the desired crystallographic orientation, e.g., epitaxial orien is deposited by ion-beam-assisted deposition. Such a com tation, of materials such as YBCO, SrRuO3, PZT, Bal_xSrxi 50 posite structure can serve as a support for deposition of sub TiO3, LaO_7SrO_3MnO3, and Si, extensive Work has focused on sequent high quality epitaxial thin ?lm layers of high tem the underlying structure or substrate onto Which the oriented perature superconducting materials. layers are deposited. BRIEF DESCRIPTION OF THE DRAWINGS Stronium ruthenate (SrRuO3 or SRO) is a conductive metal oxide material and it has been used as an electrode in ferro 55 FIG. 1 shoWs a graph plotting critical current density (in electric capacitor applications. Epitaxial SrRuO3 thin ?lms MA/cm2) for 1.5 micron thick YBCO coatings upon various have been previously deposited upon stronium titanate (Sr SrTi,€Ru1_,€O3 Where 0<x§1 buffer layers in accordance With TiO3 or STO) substrates (see, Chen et al., “Epitaxial SrRuO3 the present invention. thin ?lms on (001) SrTiO3,” Appl. Phys. Lett., 71 1047 FIG. 2 shoWs a graph plotting critical current density (in (1997). Strontium titanate is a dielectric oxide and has been MA/cm2) for 1.5 micron thickYBCO coatings upon a stron previously described as a suitable base substrate, e. g., in US. tium titanate (SrTi,€Ru1_,€O3 Where x:1) buffer layer depos Pat. No. 6,541,136. Stronium titanate has also been previ ited at various temperatures. ously described as a buffer material in superconductive struc tures, e.g., in US. Pat. No. 6,562,761 Wherein strontium DETAILED DESCRIPTION titanate is suggested as a buffer layer on selected metal sub 65 strates and selected single crystal substrates, and in other The present invention is concerned With buffer layers of microelectronic structures, e.g., in US. Pat. No. 5,471,364 SrTi,€Ru1_,€O3 Where 0<x<1 for subsequent deposition of thin US 7,736,761 B2 3 4 ?lm materials and composite structures for subsequent biliZed Zirconia (YSZ), cerium oxide (CeOZ), europium growth of thin ?lm layers thereon. The present invention is oxide, nickel aluminate spinel (N iAl2O4), and barium Zircon further Concerned With composite structures including a ate (BaZrO3). Preferably, the layer of metal oxide or metal buffer layer of SrTi,€Ru1_,€O3 Where 0<x§1 on a base metllic oxynitride material is yttrium oxide, aluminum oxynitride, substrate including a layer of magnesium oxide thereon. erbium oxide or yttria-stabiliZed Zirconia and more prefer These composite structures can be subsequently coated With ably is yttrium oxide or erbium oxide.
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