PATN Patent Bibliographic Information WKU Patent Number: 05356872 SRC Series Code: 8 APN Application Number: 2157780 APT Application Type: 1 ART Art Unit: 112 APD Application Filing Date: 19940317 TTL Title of Invention: "Method of making high Tc superconducting thin films with fullerenes by evaporation" ISD Issue Date: 19941018 NCL Number of Claims: 5 ECL Exemplary Claim Number: 1 EXP Primary Examiner: King; Roy V. NDR Number of Drawings Sheets: 2 NFG Number of Figures: 3 INVT Inventor Information NAM Inventor Name: Eidelloth, deceased; Walter CTY Inventor City: late of Yorktown STA Inventor State: NY INVT Inventor Information NAM Inventor Name: Busch, legal representative; James T. CTY Inventor City: Arlington STA Inventor State: VA INVT Inventor Information NAM Inventor Name: Gambino; Richard J. CTY Inventor City: Yorktown Heights STA Inventor State: NY INVT Inventor Information NAM Inventor Name: Ruoff; Rodney CTY Inventor City: Menlo Park STA Inventor State: CA INVT Inventor Information NAM Inventor Name: Tesche; Claudia D. CTY Inventor City: Helsinki CNT Inventor Country: FIX ASSG Assignee Information NAM Assignee Name: The United States of America as represented by the Secretary of the Navy CTY Assignee City: Washington STA Assignee State: DC COD Assignee Type Code: 06 RLAP Related U.S. Application Data COD Parent Code: 74 APN Application Number: 98094 APD Application Filing Date: 19930728 PSC Parent Status Code: 01 PNO Patent Number: 5332723 CLAS Classification OCL Original U.S. Classification: 505474 XCL Cross Reference Classification: 505473 XCL Cross Reference Classification: 505730 XCL Cross Reference Classification: 505732 XCL Cross Reference Classification: 505785 XCL Cross Reference Classification: 427 62 XCL Cross Reference Classification: 427596 XCL Cross Reference Classification: 4271263 EDF International Classification Edition Field: 5 ICL International Classification: B05D 306 ICL International Classification: B05D 512 ICL International Classification: C23C 1400 FSC Field of Search Class: 505 FSS Field of Search Subclass: 473;474;785;730;732 FSC Field of Search Class: 427 FSS Field of Search Subclass: 62;63;126.3;596 UREF U.S. Patent Reference PNO Patent Number: 5196396 ISD Issue Date: 19930300 NAM Patentee Name: Lieber OCL Original U.S. Classification: 505460 UREF U.S. Patent Reference PNO Patent Number: 5294600 ISD Issue Date: 19940300 NAM Patentee Name: Tanigaki et al. OCL Original U.S. Classification: 505100 UREF U.S. Patent Reference PNO Patent Number: 5324495 ISD Issue Date: 19940600 NAM Patentee Name: Gorun OCL Original U.S. Classification: 423439 FREF Foreign Reference PNO Patent Number: 5-17114 ISD Issue Date: 19930100 CNT Foreign Reference Country Code: JPX OREF Other Reference Okuda et al, "Preparation of Alkaline-metal-doped C.sub.60 Superconducting ilm and its Stabilization in Air with protective coatings", Jpn. J. Appl. Phys. vol. 33 (1994) pp. 1851-1855. R. B. van Dover, et al.; "Critical Currents Near 10.sup.6 A cm.sup.-2 at 77K in Neutron-Irradiated Single-Crystal YBa.sub.2 Cu.sub.3 O.sub.7 "; Nature, vol. 342 2 Nov. 89; pp. 55.57. L. Civale, et al.; "Defect Independence of the Irreversibility Line in Proton-Irradiated Y-Ba-Cu-O Crystals"; 27 Aug. 90; Physical Review Letters; 6519 Aug. 1990 pp. 1164-1167. T. K. Worthington, et al.; "Anisotropic Nature of High-Temperature Superconductivity in Single-Crystal Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x "; The American Physical Society; 59(10) Sep. 1987 pp. 1160-1163. T. T. M. Palstra, et al; "Angular Dependence of the Upper Critical Field of Bi.sub.2.2 Sr.sub.2 CA.sub.0.8 Cu.sub.2 O.sub.8+.delta. ", Physical Review; 38(7) Sep. 1988 pp. 5102-5105. LREP Legal Information FR2 Combined Principal Attorney(s): Busch; James T. FR2 Combined Principal Attorney(s): McCarthy; William F. FR2 Combined Principal Attorney(s): McDonald; Thomas E. ABST Abstract An evaporation method of producing a new high Tc superconducting material using fullerene molecules as artificial pinning sites for any magnetic flux that may enter the material. PARN Parent Case Text This application is a division of application Ser. No. O8/09,804, filed 28 Jul. 1993, now U.S. Pat. No. 5,332,723. BSUM Brief Summary BACKGROUND OF THE INVENTION For most applications of superconductors the critical current density is the true figure of merit--the higher the better. In type II superconductors such as the high-T.sub.c materials, magnetic flux can easily enter the body of the material, i.e., the lower critical field H.sub.c1 is very small. It is important to "pin" such magnetic flux because motion of flux lines implies dissipation. Such pinning action occurs naturally at any sort of defect in the material. There are various techniques to improve the critical current density by introducing artificial defects; irradiation of thin films with neutrons as described by Van Dover et al., Nature, 55, 1989, and with protons as described by T. K. Worthington et al., Phys. Rev. Lett. 65, pg. 1164, 1990 have been reported. The creation of more pinning sites is reasonable as long as the critical current density is limited by flux depinning. Other methods of artificially increasing the defect density have also been tried including ion irradiation and cation substitution. SUMMARY OF THE INVENTION Our invention uses a new technique to create artificial pinning sites in high-T.sub.c thin films during the film growth with the help of the recently discovered C-60 molecules. These molecules can be deposited simultaneously as the thin film is grown. Their chemical potential will prevent a direct reaction of atomic carbon with the high-T.sub.c thin film which would be detrimental to the superconducting properties of the film. However, the C-60 molecules will act as localized defects and they will form excellent pinning sites. Disruption of the superconducting wavefunction can at best occur on a length scale comparable to the coherence length. Therefore it is imperative to create defects of this size. The diameter of the C-60 molecules coincides very well with measured values of the coherence lengths in high-T.sub.c materials. In this regard see T. K. Worthington et al., Phys. Rev. Lett. 59, pg. 1160, 1987 and T. T. M. Palstia et al., Phys. Rev. B38, pg. 5102, 1988. As other carbon cage "fullerene" molecules exist, it is implied that they could also be employed. A steady gradation of carbon cage diameters is therefore available, and this allows some control of the nature of the pinning site. One object of our invention is to create a new superconducting material which has a high critical current density. Another object of our invention is to provide the steps necessary to make a high critical current density superconducting material. A further object of our invention is to utilize the newly discovered fullerene molecules, i.e., C.sub.60, C.sub.70 etc., as artificial pinning sites in a superconducting material so that magnetic flux lines are relatively motionless. DRWD Drawing Description DESCRIPTION OF THE DRAWINGS FIG. 1(a) depicts a cuprate superconductor matrix with fullerene molecules therein which is on a single crystal substrate. FIG. 1(b) shows an improved thin film superconductor in which the mixed cuprate and fullerenes are deposited in alternate layers and are aligned crystallographically with the single crystal substrate. FIG. 2 is a side view of the apparatus used to make the improved thin film superconductor. DETD Detail Description DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the FIGS. 1 and 2 wherein like numbers refer to the same elements. FIG. 1(a) shows a superconductor cuprate matrix 11 which is mixed with fullerene molecules and is atop a substrate 10. This is the superconductor which results from the method described now with relation to FIG. 2. There is shown a pulsed laser 13 preferably of the excimer type which operates at a wavelength of about 248 nanometers. The laser beam is focused through lens 14 and beamed through a window 15 of quartz glass into vacuum chamber 16. Any suitable vacuum pump 17 can be used to evacuate the chamber 16. The cuprate target 12 is placed in the vacuum chamber 16 with a partial pressure of about 200 mTorr O.sub.2 supplied from an oxygen source 24. As the laser beam strikes the target source 12 a plume of cuprate 22 is deposited on the substrate 20. Placed near the target 12 is a fullerene, such as C.sub.60, powder 18 in a tungsten boat 19. C.sub.60 sublimes in a vacuum at about 350.degree. C. so by heating the boat 19 to a temperature of about 350.degree. C. a source of C.sub.60 molecules are delivered to the substrate 20 surface at a controllable rate by moving the shutter 23 as desired. The tungsten boat is generally heated by suppling an electrical current through the boat from any convenient source which has not been shown in FIG. 2 for the sake of clarity. C.sub.60 is known to be stable in a gas phase at 800.degree. C. and is likely stable at ever higher temperatures. The substrate 20 is a single crystal material which in our preferred embodiment is strontium titanate (SrTiO.sub.3). Other single crystal materials such as lanthanum gallate (LaGaO.sub.3) or magnesium oxide (MgO) could also be used. The substrate 20 is heated by any conventional heater 21 to a temperature of about 750.degree. C. In our preferred embodiment evaporation from the cuprate target source 12 and the fullerene source 18 occurs simultaneously so that the vapor from both sources is deposited on the substrate 20 to form a solid. The C-60 can also be delivered in a controllable way so as to produce novel layered structures. Such alternate flux pinned/flux not pinned multilayer structures could have novel properties. CLMS Claims STM Claim Statement: We claim: NUM Claim Number: 1. 1. A method of making a high temperature superconductor comprising the steps of providing an evacuated chamber containing a partial pressure of oxygen between 10 and 300 mTorr, suppling in said chamber a solid source of a cuprate high temperature superconductor, a source of fullerene molecules and a substrate, and simultaneously evaporating from both sources so that the vapor from both sources is deposited on said substrate to form a cuprate high temperature superconductor thin film. NUM Claim Number: 2. 2. The method of claim 1 wherein said source of cuprate high temperature superconductor is evaporated by laser ablation. NUM Claim Number: 3. 3. The method of claim 1 wherein said source of fullerene molecules is C.sub.60 powder heated to 350.degree. C. in a tungsten boat. NUM Claim Number: 4. 4. The method of claim 3 wherein said substrate is a single crystal of SrTiO.sub.3 heated to 750.degree. C. NUM Claim Number: 5. 5. The method of claim 4 in which a shutter means is used to control the vaporization of the C.sub.60 powder so as to obtain an alternate flux pinned/flux not pinned multilayer structure on said substrate of cuprate and C.sub.60 molecules.