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  Multilayer composites and manufacture of sameUSPTO Application #: 20060124447Title: Multilayer composites and manufacture of same Abstract: The present invention is directed towards a process of depositing multilayer thin films, disk-shaped targets for deposition of multilayer thin films by a pulsed laser or pulsed electron beam deposition process, where the disk-shaped targets include at least two segments with differing compositions, and a multilayer thin film structure having alternating layers of a first composition and a second composition, a pair of the alternating layers defining a bi-layer wherein the thin film structure includes at least 20 bi-layers per micron of thin film such that an individual bi-layer has a thickness of less than about 100 nanometers. (end of abstract) Agent: University Of California Los Alamos National Laboratory - Los Alamos, NM, US Inventors: Terry G. Holesinger, Quanxi Jia USPTO Applicaton #: 20060124447 - Class: 204192110 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Coating, Forming Or Etching By Sputtering, Ion Beam Sputter Deposition The Patent Description & Claims data below is from USPTO Patent Application 20060124447. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0002] The present invention relates to a process and targets for the controlled deposition of multilayer films, e.g., multilayer high temperature superconducting (HTS) films, films having functionally graded compositions, e.g., HTS films having functionally graded compositions, and films doped with minor amounts of a second material, e.g., HTS films doped with minor amounts of a second material. BACKGROUND OF THE INVENTION [0003] One conventional process for the deposition of superconducting thick films, such as YBCO, and other industrial films such as semi-conductor films, ferroelectric films, insulating or optical coating films, and the like, is pulsed laser deposition (PLD). In such a process, a target, typically a disk-like shaped target, of the material or materials to be deposited is contacted with a laser beam of the desired energy and frequency. Commonly, such a disk-like target is rotated during the process to avoid contacting only a single spot of the target. In some PLD processes, a laser beam is simply rastered across sections of a target so that it is the laser beam that is moved rather than the target. [0004] Since initial development, coated conductor research on HTS superconductors has focused on fabricating increasing lengths of the material, while increasing the overall critical current carrying capacity. Different research groups have developed several techniques of fabricating coated conductors. Regardless of which techniques are used for the coated conductors, the goal of obtaining highly textured superconducting thick films, such as YBa.sub.2Cu.sub.3O.sub.7-x (YBCO), with high supercurrent carrying capability on metal substrates remains. The use of thick superconducting films for coated conductors appears logical because both the total critical current and the engineering critical current density (defined as the ratio of total critical current and the cross-sectional area of the tape) are directly correlated with the thickness of the superconducting films. Multilayer HTS films have recently been shown to yield high current superconducting composites because high quality, thick HTS coatings can be grown with multilayers. [0005] U.S. Pat. Nos. 5,356,522 and 5,580,667 by Lai et al. describe the use of sectored targets in the preparation of thin film magnetic disks. Their sectored targets are designed for deposition via sputtering as the target moves consecutively linearly through successive regions of the sputtering system. They do not describe sectored disks, do not describe rotation of sectored targets during deposition, and do not describe deposition of high temperature superconducting materials. SUMMARY OF THE INVENTION [0006] In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a process of depositing multilayer thin films by rotating a single target having at least two segments with differing compositions under a processing beam to generate processed material from the single target for deposition of the processed material upon a substrate, the processing beam contacting the segments with differing compositions in a controlled defined manner, and contacting the processed material from the single target with the substrate under conditions sufficient to deposit the processed material upon the substrate, where processed material from the segments with differing compositions is deposited in a predetermined defined manner as a multilayer thin film. The segment compositions can be single component or multicomponent materials. [0007] In another embodiment, the present invention provides a process of depositing multilayer thin films by contacting a single target having at least two segments with differing compositions under a processing beam in a controlled defined manner thereby generating processed material from the single target for deposition of the processed material upon a substrate, and contacting the processed material from the single target with the substrate under conditions sufficient to deposit the processed material upon the substrate, where processed material from the segments with differing compositions is deposited in a predetermined defined manner as a multilayer thin film. The segment compositions can be single component or multicomponent materials. [0008] Further, the present invention provides a disk-shaped target for deposition of multilayer thin films by a pulsed laser or pulsed electron beam deposition process, such a disk-shaped target including at least two segments with differing compositions. The segments can be single component or multicomponent materials. [0009] Further, the present invention provides a multilayer thin film structure having alternating layers of a first composition and a second composition, a pair of the alternating layers defining a bi-layer wherein the thin film structure includes at least 20 bi-layers per micron of thin film such that an individual bi-layer has a thickness of less than about 50 nanometers. In another embodiment, the alternating layers can include more than two compositionally different layers such that a tri-layer, quad-layer or the like is defined and the thin film structure can include a large multiple of such tri-layers, quad-layers or the like per micron of thin film. BRIEF DESCRIPTION OF THE FIGURES [0010] FIGS. 1(a)-(i) show exemplary configurations for targets in accordance with the present invention. [0011] FIG. 2 shows a film structure obtainable with a sectored target when deposition parameters are varied during deposition in accordance with the present invention. [0012] FIG. 3 shows a plot of field dependent measurements of superconducting properties of various multilayer films produced in accordance with the present invention. DETAILED DESCRIPTION [0013] The present invention is concerned with targets and a process for the preparation of multilayer films, e.g., high temperature superconducting (HTS) films, films having functionally graded compositions, e.g., HTS films having functionally graded compositions, and films doped with minor amounts of a second material, e.g., HTS films doped with minor amounts of a second material. The applications of the present invention are widespread. Not only is it very applicable to the superconductor industry, but also of interest to other film-related industries for films such as semiconductors, ferroelectrics, magnetic coatings, magnetoresistance materials, thermoelectrics, insulators, optical coatings and the like. Multilayer structures with repeating layers have been previously described for magnetic films of, e.g., Pt/Co, PdCo and the like and for such films using intermediate insulating layers of SiO.sub.2 and the like, for giant magnetoresistance structures of, e.g., alternating ferromagnetic and non-magnetic layers, for thermoelectric materials such as trilayer structures of repeating layers of PbTe, PbSeTe and Te and the like, and semiconductor structures of, e.g., repeating trilayers of InAs, GaSb and AlSb and the like. Each such previous structure may be prepared using the process and sectored target of the present invention by properly designing the target and process. [0014] The present invention allows the growth of high-density multilayer structures sometimes referred to as superlattice-like structures. The term "superlattice structure" refers to a composite structure made of alternating ultrathin layers of different component materials. A superlattice structure typically has an energy band structure which is different than, but related to, the energy band structures of its component materials. The selection of the component materials of a superlattice structure, and the addition of relative amounts of those component materials, will primarily determine the resulting properties of a superlattice structure as well as whether, and by how much, those properties will differ from those of the individual component materials a superlattice structure. [0015] The process of the present invention can allow preparation of multilayer composites with a wide range of thicknesses with from a single unit (of alternating layers of the different deposited materials, e.g., a bi-layer of a first composition and a second composition) up to many units with total combined thicknesses greater than, e.g., one micron. [0016] The targets and process of the present invention allow the use of only a single pulsed laser deposition (PLD) target in the preparation of multilayer films, e.g., multilayer HTS films. A target is formed prior to use to contain one or more additional sectors, regions, or other shapes that have a different composition of material relative to the primary matrix of the target as shown in FIGS. 1(a)-(i). Due to the simplistic design and easy use in existing PLD systems, the present invention offers significant advantages in terms of composition and structural control that are not readily accessible by other processes. [0017] The HTS composites are, in the broadest sense, composed of a substrate, possibly one or more buffer layers, and an HTS film, which is the functional object of the composite. The substrates can be single crystal substrates such as strontium titanate (STO) or yttria-stabilized zirconia (YSZ), textured polycrystalline substrates such as roll-textured nickel (RABiTS), or non-textured polycrystalline substrates that have a textured template film deposited on the surface such as an ion-beam-assist deposited YSZ or MgO film on a nickel alloy, e.g., a nickel-chromium alloy. Often, but not always, buffer layers are employed to facilitate the deposition of a final HTS layer. Examples of buffer materials can include cerium oxide, strontium titanate, strontium ruthenate, yttrium oxide, and lanthanum manganate (LaMnO.sub.3). The final layer can be a film or composite film that contains a desired HTS material such as YBCO (Y-123). [0018] The substrates can be other materials for other applications such as semiconductors, ferroelectrics, magnetic coatings, magnetoresistance materials, thermoelectrics, insulators, optical coatings and the like. For example, for ferroelectrics, suitable substrates can include silicon, platinum-coated silicon and other conductive material-coated silicon. For semiconductors, suitable substrates can include stainless steel, molybdenum and silicon. For magnetic coatings, suitable substrates can include silicon. For magnetoresistance materials, suitable substrates can include nonmagnetic materials such as glass, silicon, aluminum oxide (Al.sub.2O.sub.3), titanium carbide (TiC), silicon carbide (SiC), a sintered product of aluminum oxide and TiO, or ferrite. For thermoelectrics, suitable substrates can include highly insulating silicon or silicon on an insulator (SOI). [0019] The factors of pulsed laser deposition (PLD) that are important in the practice of the present invention to form desired structures include the target rotation speed, pulse rate, pulse energy, and distance from the target center to the point on the target where the laser beam is incident. Variations in these parameters in conjunction with specially designed targets can affect the periodicity and compositional makeup of the resulting film. These variations can be made between runs or changed during film deposition in either a stepwise or continuous manner. [0020] Similarly, the factors of pulsed electron beam deposition (PEBD) that are important in the practice of the present invention to form desired structures include the target rotation speed, pulse rate, pulse energy, and distance from the target center to the point on the target where the electron beam is incident. Variations in these parameters in conjunction with specially designed targets can affect the periodicity and compositional makeup of the resulting film. These variations can be made between runs or changed during film deposition in either a stepwise or continuous manner. Continue reading... Full patent description for Multilayer composites and manufacture of same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Multilayer composites and manufacture of same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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